C. A quatre dents. Bucarde Meretrice Lucine
II. Inequivalves.
1. A charnière sans dents. Acarde Radiolite Vulselle Marteau Huitre Avicule
2. A une dent. Came
3. A deux dents. Spondyle Plicatule Placune
4. A plusieurs dents. Perne
III. COQUILLES UNIVALVES.
I. Uniloculaires.
1. Sans spirale. A. En Calotte. Patelle Oscane
B. En Tube. Vermiculaire Silicaire Arrosoir
2. En spirale. A. L'ouverture entière et sans canal à sa base. Carinaire Halioïde Sigaret Stomate Argonaute Concholepas Nerite Natice Helicine
B. L'ouverture échancreée et canaliculée à sa base. Cerite Pyrule Rocher Rostelaire Strombe Buccin Casque
II. Multiloculaires.
Nautilé Orbulite Ammonite Planulite Camerine Rotulite
Turrilite Baculite Spirelle Orthocère Hippurite Belémnite.
In this system which we have exhibited, the arrangement is more methodical, and the genera are more definite, than in the Linnaean system. It unquestionably holds the first rank in the modern artificial methods.
There is a class of writers whose labours deserve some notice in this place. We allude to those who have devoted their attention to the very minute shells, so common among the sand on every sea-coast. These are too small to be examined by the naked eye, and from the instrument employed in their investigation, they are usually termed Microscopic shells. Plancus, in his work, De Conchis Ariminensibus minus notis, published in 1739, may be considered as the first who drew the attention of Conchologists to these nearly invisible objects. J. F. Hoffman, in his Dissertatioincula de Carinu Ammonis nativo Litioris Bergensis in Norvegia, published in the Transactions of the Electoral Academy of Mentz, 1757, and in his essay de Tubulis Vermicularibus Cornu Ammonis referentibus, ibid. 1761, made us acquainted with various species of minute nautili produced on the northern shores. Nor did those discoveries fail to excite interest in this country. Boys and Walker devoted their attention to the subject, and gave to the world the result of their labours, in a thin quarto, entitled Testacea Minuta variora nuperrime detecta in arena littoris Sandvicensis, London, 1784. Other observers, equally ardent and successful, have increased our knowledge of the forms of these minute bodies, particularly Soldani, who, in his Testaceographia ac Zoophytographia parva et microscopica, 1789 and 1795, exhibited many figures of the minute shells of Portoferara, &c. The late Mr Adams described the minute species which he observed on the coast of Pembrokeshire, in the third and fifth volumes of the Transactions of the Linnaean Society of London, and other species of British growth have been investigated by the author of Testacea Britannica. We shall close this list with noticing the Testacea Microscopica aliique minuta ex generibus Argonauta et Nautilus ad Naturam Picta et Descripta, Vienna, 1798. It is the joint production of L. A. Fichel and J. P. C. A. Moil, and merits an attentive perusal.
We are aware that such microscopic investigations are regarded by some Conchologists as useless, so that the minute species are excluded from their systems. But it is surely a strange method of proceeding in natural history, to judge of the merits or importance of species from their size. It is true that we are still ignorant of the inhabitants of those shells, and may long continue to be so; but our present knowledge of these has enabled us to fill up many blanks, to preserve some new relations, and even to draw some important conclusions.
That this sort of inquiry has in many instances been injudiciously conducted, all who are acquainted with the subject must admit. Due care has not been taken to distinguish these minute testacea from the fry of the larger shells, so that the number of species has been very injudiciously multiplied. These remarks apply to several figures of Walker, and to a still greater number of those of Adams. The authors of the preceding class have laboured to bring to perfection the artificial system of Conchology, and have formed their arbitrary characters, independent of the habits of life of the contained animal. But the naturalists whom we have now to consider, have traced these animals to their lurking places, and arranged them according to the situation in which they reside, instead of the forms which they exhibit.
At the head of this class of Conchologists Dr Martin Lister stands preeminently conspicuous. His great work, entitled Historia sive Synopsis Methodica Conchyliorum, was begun in 1685, and completed in 1692. It will long remain a monument of the extensive information and unrewarded diligence of its author. The following synoptical view of the work will enable our readers to comprehend its plan; the original should be consulted with care.
Lib. i. De Cochleis terrestribus. Pars 1. De Buccinis terrestribus. Pars 2. Cochleae nudae terrestris Limaces qui busdam dictae.
Lib. ii. De Turbinibus et bivalvibus aquae dulcis. Pars 1. De Turbinibus. Pars 2. De Testaceis bivalvibus fluviatilibus.
Lib. iii. De Testaceis bivalvibus marinis. Pars 1. De Testaceis bivalvibus, imparibus testis. Pars 2. De Testaceis bivalvibus, paribus testis. Pars 3. De Testaceis multivalvibus.
Lib. iv. De Buccinis marinis quibus etiam vermiculi, dentalia et patellae numerantur.
The plan followed by Sir Robert Sibbald in his Scotia Illustrata is somewhat different from that of Lister. He divides the Testacea into two classes, land and water shells, and the latter class he subdivides into fluviatile and marine. His inferior divisions are destitute of precision, and the number of his species limited.
The system of D'Argenville, which was so much esteemed and so long followed in France, is essentially the same with that of Lister in the higher divisions. The plan is indeed so simple, and in appearance so natural, that it has met with many admirers. It has even been useful in encouraging naturalists to study particular departments of the science, when they were prevented by their situation from devoting their attention to the whole. It is probably to this circumstance that we are indebted to Schröter for his observations on the land shells in the neighbourhood of Thangelstadt, and on the river shells of Thuringia.
The preceding arrangements, formed according to the situations in which the animals reside, and not according to their external coverings, may be considered as the first attempts at a natural method in Conchology. They serve as an introduction to a new class of authors, whose views may be considered as of a higher order, and to whose labours we shall devote our attention in the following section.
Section III. Systems constructed from Circumstances connected with the Form and Structure of the contained Animal.
The first attempt, of any consequence, to arrange Systems testaceous animals according to the soft parts of their bodies, was made by Adanson, in his Histoire Naturelle du Senegal, published at Paris in 1757. In this system, the ancient classes of Univalves, Bivalves, and Multivalves, are employed under the titles les Limaçons, les Conques, and les Conques Multivalves.
Classe I. Les Limaçons.
Sect. I. Les Limaçons Univalves.
Fam. 1. Les limaçons univalves qui n'ont ni yeux ni cornes. Fam. 2. Les limaçons univalves qui ont deux cornes, et les yeux placés à leur racine et sur leur côte interne. Fam. 3. Les limaçons univalves qui ont quatre cornes, dont les deux extérieurs portent les yeux sur le sommet. Fam. 4. Les limaçons univalves, qui ont deux cornes et les yeux placés à leur racine, et sur le côte externe, ou pas derrière. Fam. 5. Les limaçons univalves qui ont deux cornes et les yeux posés un peu au dessus de leur racine et sur leur côte externe.
Sect. II. Les Limaçons Operculés.
Fam. 1. Limaçons operculés qui ont deux cornes, avec un renflement, et qui portent les yeux ordinairement au dessus de leur racine, et à leur côte externe. Fam. 2. Limaçons operculés qui ont deux cornes sans renflement, et les yeux placés à leur racine, et sur leur côte externe. Fam. 3. Limaçons operculés qui ont quatre cornes, dont les deux extérieurs portent les yeux sur leur sommet.
Classe II. Les Conques Bivalves.
Fam. 1. Les conques bivalves qui ont les deux lobes du manteau séparés dans tout leur contour. Fam. 2. Les conques bivalves dont les deux lobes du manteau forment trois ouvertures sans aucun tuyau. Fam. 3. Les conques bivalves dont les deux lobes du manteau forment trois ouvertures, dont deux prennent la figure d'un tuyau assez long.
The presence or absence of an operculum or lid, gives rise, in this system, to a division of the univalves into two sections, and the families are established from circumstances connected with the number of the tentacula, and the number and position of the eyes. The families among the bivalves, are arranged according to the structure of their cloak or external covering. In the class of multivalves, which we have omitted in the table, the characters are taken from the form and structure of the shell.
The work of Geoffroy, entitled, Traité sommaire In the following year he published *Le Règne Animal*, Conchology distribué d'après son organisation, in which he arranged the mollusca according to his peculiar views, from characters drawn exclusively from the animal.
He divides the mollusca into six classes, which he terms *Cephalopoda*, *Pteropoda*, *Gasteropoda*, *Aecephala*, *Brachiopoda*, and *Cirripedia*.
In the class *Cephalopoda* the body is in the form of a sack, open above, containing the branchiae, with a distinct head, surrounded by fleshy elongations or arms, adapted for moving the body or seizing prey. Into this class, along with the Sepia of Linnaeus, Cuvier has inserted the multilocular shells of his genus *Nautilus*, and the genus *Argonauta*. But it is to be feared, that our knowledge of the testaceous mollusca which inhabit the numerous multilocular shells, is too limited to enable us to assign them their true place in a natural arrangement of animals.
In the second class, termed *Pteropoda*, the body is closed, the head is destitute of the long fleshy arms which distinguish the animals of the preceding division; two fin-like membranes, situated on the sides of the neck, and on which the branchial tissue is in general spread, serve as organs of motion. There is only one shell belonging to this class, viz., the Anomia tridentata of Forskaehl, now forming a part of the genus Hyalina.
The third class, which includes a great number of naked and testaceous mollusca, and to which Cuvier gives the name *Gasteropoda*, from the circumstance of the belly being formed for crawling, has been subdivided into seven orders, from circumstances connected with the organs of respiration.
The first and second orders, *Nudibranches* and *Inferobranches*, consist almost entirely of genera formed from the animals which Linnaeus and many others included in the genus *Doris*. They are naked mollusca, and are likewise destitute of any internal testaceous plate. The third order, termed *Tectibranches*, contain animals whose branchiae, like small leaves more or less divided, are situated on the right side, or upon the back. The animals of this division possess a shell, but it is in general placed beneath the common integuments, such as the genus *Aplysia* and several species of the genus *Bulla*. In the fourth order, termed *Pulmones*, which breathe air, he has constituted two divisions, the terrestrial and the aquatic. The animals of the former live on land, and were included by Linnaeus in his genera *Limax* and *Turbo*. They are the land shells of most authors. Those of the division, termed aquatic, live in the water, but require, at intervals, to come to the surface to obtain fresh air. They constitute, with a few exceptions, the fresh water shells of naturalists. The *Pectinibranches* form the fifth order, and are distinguished by the branchiae, which are like leaves or threads placed parallel in one, two, or three lines, on the surface of the pulmonary cavity. It includes the whole of the marine species of the Linnaean genera of turbinate univalves. Into this order Cuvier, from the consideration of other characters, has inserted the genus *Cycolostoma*, which, according to the characters indicated by the respiratory organs, belongs to the Pulmones. In the sixth order, termed Scutibranches, the branchiae are similar to those of the preceding order, but the sexes are united, each individual being capable of impregnating or being impregnated. The shells in general are cup-shaped, and destitute of a lid. It includes the genus Halyotis, and many species of the old genus Patella. In the last order, called Cyclobranches, the branchiae appear in the form of small leaves or pyramids strung round the under margin of the cloak. They enjoy a hermaphroditism similar to those of the preceding order. The species of the genus Patella which are allied to the vulgata, and the genus Chiton, are included in this order.
In the fourth class, or Acephala, he includes the bivalve shells, distributing them into families, from characters nearly similar to those which we have pointed out as having been previously employed by Poli.
The fifth class, termed Brachiopoda, contains animals, resembling those of the preceding class in having a cloak of two lobes, but these are always open. The branchiae consist of small leaves placed on the inner margin of each lobe. In place of a foot they have two retractile fleshy arms, which are extensible. This class includes the Patella unguis of Linnæus, the genus Terebratula and the Patella anomala of Müller.
The class Cirripedida, distinguished by the articulated filaments with which the animals are furnished, contains the species of the genus Lepas of Linnæus. The shells belonging to the Linnæan genera Serpula and Dentalium, are transferred to the class termed Annelides.
This system of the molluscous animals is unquestionably the most perfect of all those which have been published. But, with all its excellence, we must inform the reader, that many species, nay, whole genera, have their places assigned them in this natural method, merely because the shells occupied a similar position in the artificial system, the form of the inhabitants being unknown.
**Section IV.—Mixed Systems.**
In this section, we shall confine our remarks to the only system of this kind of any consequence which has hitherto appeared, and which is the production of Lamark, one of the most celebrated French zoologists of the present day. The *Système des Animaux sans Vertèbres*, Paris, 1801, of this author, embraces the whole range of animals included in the classes Insecta and Vermes of Linnæus. Where treating of the Mollusca he divides them into two orders. The first, termed Cephalous, from possessing a head, includes the univalves. The second, termed Acephalous; from the absence of a head, includes the bivalves. Instead of giving the outline of Lamark's system as published in the work now mentioned, we propose rather to present the reader with the abridgment of his method, as contained in his *Extrait du Cours de Zoologie*, Paris, 1812; but we anxiously look for the completion of the great work, in which he is at present engaged, *Histoire Naturelle des Animaux sans Vertèbres*, where we hope to see this system rendered still more precise and useful. It is necessary to mention, that the animals are arranged according to the perfection of their organs, beginning with the most simple.
**I. Acephales Testaces.**
Ils sont enfermés dans une coquille bivalve, qui s'ouvre et s'articule en charnière.
A. Acephalés monomyaires, leur coquille offre inté- rieurement une impression musculaire subcentrale.
a. Acephalés ayant deux bras opposés, ciliés, et qui se vouent en spirale en rentrant dans la coquille.
1. Les Brachiopodes.
| Lingule | Orbicule | |---------|---------| | Térébratule |
b. Acephalés sans bras, ne se fixant point par un byssus.
1. Les Ostracées.
| Radiolite | Huitre | |-----------|--------| | Calcéole | Gryphée | | Cranie | Plicatule | | Anomie | Spondyle | | Placune | Peigne | | Vulscle | |
c. Acephalés ayant la plupart un pied propre à filer, et se fixant par un byssus.
1. Les Byssifères.
| Houlette | Crenatule | |----------|-----------| | Lame | Perne | | Pinne | Marteau | | Meule | Avicule | | Modiole | |
B. Acephalés dimyaires, leur coquille offre interieurement deux impressions musculaires séparées et latérales.
a. Coquille inequivalve.
1. Les Camacées.
| Etherie | Corbule | |---------|---------| | Came | Coquille fixée. | | Dicerate| Pandore |
b. Coquille equivalve.
• Acephalés lamellipédés ; leur pied est aplati et lamelliforme. Ligament exterier, la coquille non baillante aux extrémités latérales.
+ Aucune dent, ou une seule dent sur chaque valve les crochets écorchés.
Les Nayades. (Coq. d'eau douce.)
Mulette Anodonte
†† Charnière multidentée.
Les Arcacées.
| Nucule | Cuculée | |--------|--------| | Petoncle | Trigonic | | Archie |
+++ Dents cardinales, grossières, et irrégulières.
Les Cardiacées.
| Iridacme | Hiatelle | | Hippope | Isocardle | | Cardite | Bucarde | Dents cardinales divergentes.
Les Conques.
Venericarde Telline Lucine Conques marines. Venus Conques Capse Cyclade Conques fluviatiles. Cytherée Donacine Galathe
** Acephales crassipedes, leur pied est épais, souvent subcylindrique. Le ligament interieur, ou la coquille baillante aux extrémités latérales.
† Ligament interieur dans une fossette.
Les Mactracees.
Erycine Maetre Onguline Lutraire Crassatelle
†† Ligament interieur, sur une dent élargie.
Les Myaires.
Anatine Mye
††† Ligament exterier. Coquille sabulicoles, non terebrantes.
Les Solenacees.
Panope Solen Glycinère Sanquinolaire
†††† Ligament exterier. Coq. terebrantes, sans pieces accessoires.
Les Lithophages.
Saxicave Petricole Rupicole Rupellaire
††††† Ligament exterier ou inconnu. Coquilles terebrantes, avec une ou plusieurs pieces accessoires, distinct des valves.
Les Pholadaires.
Pholade Clavagelle Taret Arrosoir Fistulane
II. MOLLUSQUES CEPHALES.
Mollusques Cephalos Gasteropodes.
A. Branchies exterier, placees sous le rebord du manteau, et disposées en serie longitudinale entre ce rebord et celui du pied. Elles ne respirent que l'eau.
Les Phyllidiens.
Pleurobranche Ombrelle Phylidie Patelle Oscabron Haliotoide
B. Branchies exterieres, composées d'une ou deux pieces placées au-dessus du cou, sous le manteau. Elles ne respirent que l'eau.
Les Calyptraiciens.
Cabochoon Calyptree Fisurelle Crepidule Emarginule
C. Branchies cachées ou couvertes, mais en saillie dans un cavite particulière. Elles ne respirent que l'eau.
Les Laplysiens.
Acere Sigaret Bullée Dolabelle Bulle Laplysie
D. Branchies cachées dans un cavite particulière, et etendues sans saillie sur les parois de la cavite. Elles ne respirent que l'air libre.
Les Linaciens.
Onchide Vitrine Parmacelle Testacelle Limace
Mollusques Cephalos Trachelipodes.
A. Sans siphon saillant, et respirant en general par un trou. Coq. a ouverture entiere, n'ayant à sa base ni canal ni veritable echancrure.
a. Ne respirant que l'air. Leur branchies sont tendues sur les parois de la cavite branchiale, sans y former de saillie.
* Tentacles cylindres : coquille terrestre, avec ou sans opercule.
Les Colimaces.
Helix Quatre Bulime Quatre Helicelle Amphibuline tentacules Agathine les Maillot
Cyclostome Vertigo Deux tentacules Auricula
** Tentacles aplatis : coquille d'eau douce toujours sans opercule, et dont l'animal vient respirer l'air à la surface de l'eau.
Les Lymneens.
Lymnee Planorbe Physè Conovule
b. Ne respirant que l'eau. Leurs branchies forment des parties saillantes dans la cavite branchiale. Les uns sont fluviatiles, les autres marine.
* Coquille fluviatile, dont le bord gauche de l'ouverture n'imité pas une demi-cloison.
† Coquille operculée dont les bord de l'ouverture sont disunis.
Les Melaniens.
Melanie Pirène Melanopside
†† Coquille operculée, dont les bord de l'ouverture sont reunis.
Les Peristomiens.
Paludine Ampullaire Valvée
** Coquilles fluviatiles ou marine, dont le bord gauche de l'ouverture imite une demi-cloison. Point de columelle ; un opercule. Les Neritacées.
Navicelle fluvatile. Nerite marine. Neritine Natice
Coquilles marine, dont le bord gauche de l'ouverture n'imite pas une demi-cloison. † Coquille flottante. Janthine.
Des plis à la columelle.
Les Plicaces.
Tornatille Pyramidelle
Ouverture obronde à bords réunis.
Les Scalariens.
Vermet Dauphinule Scalare
Ouverture évasée, à bord désunis.
Les Macrostomes.
Stomate Stomatelle
Ouverture non évasée, à bord disunis.
Les Turbinacées.
Turritelle Monodonte Phasianelle Cadran Turbo Troque
B. A. Siphon saillant. Ils sont tous marins, car- nassiers, et ne respirent que l'eau, qui parvient aux branchies par un siphon. Ouverture de la coquille, soit canaliculée, soit échancrée ou versante à sa base.
Un canal plus ou moins long à sa base de la coquille ; le bord droit de l'ouverture ne changeant point de forme avec l'âge.
Les Canalifères.
Cerite Pyrule Pleurotome Fuseau Clavatule Murex Turbinelle Ranelle Fasciolaire Strutholaire
Un canal plus ou moins long à la base de la coquille ; le bord droit de l'ouverture changeant de forme avec l'âge, et ayant un sinus inférieurement.
Les Ailées.
Rostellaire Strombe Pterocere
Canal nul ou très court. Un échancrure oblique à la base de l'ouverture.
Les Purpurifères.
Casque Buccin Cassidaire Concholepas Harpe Pourpre Tonne Monoceros Vis Ricinule Eburne Nasse
Point de canal à la base, mais une échancrure plus ou moins grande. Des plis sur le columelle.
Les Columellaires.
Cancellaire Volute Colombelle Marginelle Mitra Volvière
Point de canal : tour de spire larges, comprimés, et enroulés de l'axe de manière que le dernier recouvre presqu'entièrement les autres.
Les Enroulées.
Ovule Ancillaire Porcelaine Olive Tarrière Cone
Mollusques Cephalis Cephalopodes.
A. Testaces polythalames.
Coquille multiloculaire à cloisons simples : leurs cloisons simples sur les bords, n'offrent point des sutures découpées et sinueuses, sur la paroi interne du test.
Coquille droite ou presque droite, point de spirale.
Les Orthocérées.
Belémnite Nodosaire Orthocère Hippurite
Coquille partiellement en spirale ; le dernier tour se terminant en ligne droite.
Les Lituolées.
Spirule Lituole Spiroline
Coquille semi-discoïde, à spirale excentrique.
Les Cristacees.
Renulite Orbiculine Cristellaire
Coquille globuleuse, sphéroïdale ou ovale : à tours de spirale enveloppans, ou à loges réunies en tunique.
Les Spherulées.
Miliolite Melonite Gyrogonite
Coquille discoïde, à spirale centrale, et à loges rayonnantes du centre à la circonférence.
Les Radiolées.
Rotalie Placentule Lenticuline
Coquille discoïde, à spirale centrale, et à loges qui ne s'étendent pas du centre à la circonférence.
Les Nautilacées.
Discorbis Nummulite Siderolite Nautilé Vorticale
Coquille multiloculaire à cloisons découpées sur les bords. Les cloisons, sinueuses et lobées dans leur contour, se réunissent contre la paroi interne du test, et s'y articulent en sutures découpées comme de feuilles de persil. The authors of the first class of Conchologists which we have mentioned, employ exclusively the characters furnished by the shell, and scarcely deign to tell us that there is an animal attached to that shell. The authors of our third class are anxious to keep the shell out of view, and draw their distinctions from the animal; but they have failed in the attempt. In extreme cases, the characters of the shell are resorted to in the absence of distinctions furnished by the animal.
Lamark perceived the inconvenience of separating these two modes of examining molluscous animals, and fortunately formed a very natural combination. We shall give his character of the genus Patella, as a specimen of this mixed system.
*Patelle, Patella.* Coquille univalve, non spirale, ovale, ou suborbiculaire, en bouclier ou en bonnet, concave et simple en dessous, entière à son sommet, et sans fissure à son bord.
*Patellier:* Gasteropode à tête tronquée obliquement, munie de deux tentacules pointues. Les yeux à la base extérieure des tentacules. Les branchies placées autour du corps, sous le rebord du manteau.
In this manner the generic character is dependent equally on the shell and the contained animal, and that genus in a system is consequently not sufficiently established in which both these characters are not included. How many genera are in this imperfect state! Were the same plan followed in the description of species, everything we could wish for would be detailed; and our knowledge of the forms of molluscous bodies would approach to perfection. How much is it to be wished, that this plan of Lamark's were generally adopted in this country! Conchology would assume a new aspect, and the number of its votaries would rapidly increase.
The reader will have perceived, in the course of the hasty review of those systems which we have enumerated, that we have refrained from making any remarks on their comparative excellence. This deficiency we now propose to supply in the following observations.
The authors that have arranged testaceous bodies, without reference to the animals that reside in them, appear to have mistaken the house for the inhabitant, and the thing formed for the being that produced it. They have torn asunder objects which are closely related, and united others which differ in structure and economy. These are necessary consequences of an artificial system, and they become more obvious in proportion as we descend in the scale of being.
The examination of shells, according to this method, may be viewed as the study of the osteology of the Mollusca. It has not for its object the investigation of living matter, but of dry bones. Nor has it any of those advantages which result from the study of the osteology of the vertebral animals. A knowledge of the bones of these animals enables us to ascertain many of their primary functions, the nature and extent of their powers of motion, and even the food on which they subsist. But our knowledge of shells merely, enables us not to say, whether the animal can crawl or swim; whether it feeds on plants or animals. The reason is obvious. All the muscles inserted upon the shell are either mere organs of adhesion, or destined to open and shut the valves. None of those muscles connected with any of the primary organs have any connection with the shell. That the shell furnishes several important characters, we readily grant; but we are here reasoning against the propriety of attending to the shell, to the exclusion of the animal, and, to this extent, our reasoning appears to be conclusive.
We are aware, that, in the other departments of natural history, the appearances which the external parts of an animal exhibit are constantly employed in the construction of orders and genera, and all the intermediate divisions. Thus, for example, the bill, feet, and feathers of birds, furnish the characters by which they are arranged in the system. Here, however, it must be observed, that the combined information yielded by these parts, makes us acquainted with the habits and organization of a bird. By means of these we can judge, and with certainty, not merely of its internal structure, but the places which it frequents, and the food which it consumes. Hence these characters may be applied with equal propriety in an artificial as in a natural method. But what opinion would we form of that Ornithologist, who could readily inform us that the cormorant has fourteen tail feathers, and the shag only twelve, but who was ignorant of the haunts of these birds, their food, and the number of their young? We might prize him as a companion in surveying a museum, but he is alike a stranger to science and nature.
Nor can we feel more respect for the student of mere shells. He may be able to tell us the number of whorls in a spiral univalve, or the form of the hinge in a bivalve; but if he knows not the nature of the organs of respiration, digestion, and reproduction of the animal to which the shell belongs, and contentedly remains in this ignorance, he has yet to learn the value of method in natural history. He cherishes with mistaken fondness the maxim of Linnaeus, "Nomina nosse oportet qui rem scire velit," while he overlooks a more important object, expressed in the motto of the Linnaean Society, "Naturae discere mores."
These remarks apply to the conchological labours of Linnaeus and his followers, who have devoted their whole attention to the arrangement of the shells, without attending to the animals. We know that some of the admirers of the Swedish naturalist presume to say, "But our great author was not wholly inattentive to the creatures for which the beautiful and endlessly diversified receptacles that he had characterized were designed. Among the generic marks was included the name of the molluscous inhabitant; or, where the animal differed from any which had a place in other parts of his system, he described it at length." (Linn. Trans. Vol. VII. 175.) Now, to what does all this attention of Linnaeus amount? In all the species which he has described, he has only noticed the animals of four of these, and in a very slight manner; and, with regard to the name of the molluscous inhabitant which he included in his generic marks, we hesitate not to say, that by this union he has betrayed carelessness. To many British ears these terms may sound harsh, but the proof of their correct application in the present instance will be abundantly evident, if we examine the references to the animals of a few of his genera. The genus Chiton is thus characterized— "Animal Doris. Testae plures, longitudinaliter gestae, dorso incumbentes." Are we not led to conclude from this character, that the animals of the Chiton exactly resemble the animals of the Doris genus, with the addition of the shells? If this be the case, how artificial is that system which places these two genera in separate orders! Upon turning, however, to the genus Doris among his vermes mollusca, we find the following characters assigned to it—"Corpus repens, oblongum, subtus planum. Os antice subtes. Anus postice, supra cinctus ciliis. Tentacula duo, supra corpus antice intra foramina retractilia." Now, the fine fringes around the anus of the Doris, which are the branchiae of the animal, and form the essential character of the genus, are not to be found in the animals of the Chiton, whose branchiae are in the form of little leaves placed along the margin of the body, and the anus is a simple pore.
According to the generic character of the Mya, the animal is an Ascidia, with the appendage of a shell. Upon turning to the genus Ascidia, we find it said "Corpus fixum, teretiusculum, vaginans. Aperturae binae, ad summitatem; altera humilior." To prove the impropriety of referring the animal of the Mya to the genus Ascidia, we shall only mention, that the former has a foot, and possesses a locomotive power,—the latter has no foot, remains immovably attached for life upon the substance to which it first adhered, and depends on the accidental bounty of the waves for all its nourishment.
The animals of nearly all the univalves are represented as belonging to the genus Limax. But, with the exception of the restricted genus Helix and Bulimus, the animals of the univalves are all generically different from the Limax. Their tentacula are generally two in number, with the eyes at the base; while the tentacula are four in the Limax, with the eyes at the tips of the two longest. These examples will suffice to establish a truth so palpably obvious.
The principal objection against this system of employing the shell, to the exclusion of the animal, arises from the fact, that nature has not drawn a line of distinction between the mollusca and the testacea. Thus, many of the vermes mollusca of Linnaeus include shells in their bodies, as the Aplysia; and many of his vermes testacea likewise are soft on the outside, the shell being inclosed by the integuments, as the Helix Haliotidea.
We have another objection to this artificial system, and one which we consider of great force; that, wherever it prevails, the form and habits of the animal are overlooked. How fully is this truth illustrated in the works of the Testaceologists of this country! We might examine all their writings, from the Pinax of Merret to the Descriptive Catalogue of Maton and Racket, including the works of Pennant, Berkenhout, Da Costa, and Donovan, and learn little more, besides the habitat, than that to every shell there is an animal attached. Of this charge the names of Lister and Montagu stand acquitted. The former has given us several good dissections, and the latter minute descriptions, of the testaceous animals.
While, in the preceding remarks, we have objected to all arrangements taken exclusively from the characters of the shell, we also disapprove of those systems founded exclusively on the characters of the animal. By the former class of methodists, the simplicity of nature is sacrificed to their peculiar views, and, by the latter, practical utility is disregarded. Devoting their whole attention to the animal, the latter Conchologists have overlooked the house in which it resides,—the roof which shelters it from the blast,—and the walls which guard it from its foes. The former Conchologists possessed very limited views of nature, and erected systems obviously artificial. To the systems of the latter, the same objections will apply. Thus, for example, among the univalves of Adanson, the families are formed from the position of the eyes chiefly. That the black points which we witness at the tips or the base of the tentacula are actually eyes, we readily admit; but what influence has these eyes on the habits of the animal? or rather, does a change of position of these organs occasion a corresponding change in the habits of the animal? Unless this is answered in the affirmative, we must consider such characters as equally artificial with any employed by Linnaeus or his followers, since they have no relation to any of the primary functions of life.
The employment of characters taken exclusively from the animal is attended with so many practical difficulties, that it never can be introduced into general practice. If we find a shell thrown ashore, the animal may be dead, or it may refuse for a time to display its organs, and prevent us from arriving at its name and history. This defect, however, is partly remedied when we can call to our aid the characters furnished by the shell.
Another objection against this method arises from the well known difficulties attending the preservation of the molluscous animals. To dry them, destroys their form and texture; to inject them, is impracticable; and when put into spirits of wine, they generally appear a shrivelled mass. But the coverings of these animals are durable, and, since they form a part of the animal,—since they are produced at first along with it, increase by the addition of new matter from its body, and continue attached to it for life,—we must condemn any classification from which the shell is excluded.
From these remarks, it will be obvious, that we consider the mixed system as the most natural and the most useful. It possesses all the advantages to which the other systems lay-claim, while it is free from their defects. It withdraws part of our attention from the shell, because it is destitute of peculiar vessels, and possesses no vital energy, to fix it on those organs of the animal which are subservient to its existence. It leads us to examine the whole animal, instead of certain parts of it merely, and has a tendency to excite us to become acquainted with the manners of a tribe, from which, imperfect and artificial systems have hitherto withdrawn our attention.
It is of the utmost importance in the formation of any arrangement of natural bodies, to have an exact idea of the relative value of the characters used, and of their true subordination. This is a subject of vast moment, and too little attended to by naturalists. We do not here consider that character as of the highest kind, which is the most general, but that which has the greatest influence over the faculties and instincts of the animal. Had this subject been studied with greater care, the science of Conchology would, at this period, have been in a more flourishing condition. To ascertain, in some degree, this subordination of character, is the object of the following observations.
The division of the testaceae mollusca into three orders, as adopted by Linnaeus, is confessedly artificial. The Multivalvia of that author possess no characters in common, neither can they boast of a general resemblance. The first genus, Chiton, consists of animals which belong to the cephalous and gastropodous mollusca. The animals of the genus Lepas approach more nearly to the crustacea than the mollusca; while the animals, inhabiting the genus Pholas, belong to the acephalous mollusca, and are closely connected with the Mya and Solenes. The shells of the first genus are merely calcareous scales, arranged transversely on the back of the animal. The shells of the second genus are variously articulated, fixed, and either sessile or pedunculated. The shells of the third genus are bivalves, with a few accessory calcareous plates. It is to be hoped that modern Conchologists will avoid so incongruous a combination.
The two remaining divisions of Linnaeus, the bivalves and univalves, are not only obvious, but natural. They indicate the existence of certain forms peculiar to the animals whose shells are thus separated in the system. The univalve shells are inhabited by animals which possess a head, and whose organs of motion are either tentacula, situated on the head, or a foot spread over the belly, as in the slug. The animals of the bivalve shells, on the other hand, are destitute of a head; some of them have no locomotive power; and, in others, the organ of motion is a fleshy foot, which the animal can protrude at pleasure. These circumstances point out the connection which subsists between the organs of the animal, and the external forms of the shell; a connection which, in every system, ought to be carefully attended to.
It is somewhat difficult to point out, among the univalves, the true subordination, or relative importance of the characters employed by Conchologists in describing them. We have much to learn of their anatomy, and hence we cannot with certainty point out the relation of the parts of the shells to the organs which those parts protect. The form and structure of the mouth, however, may be expected to furnish characters of the first-rate importance, and have always attracted the notice of the student of testaceous bodies. The very shape of the animal, together with its ordinary habits, must necessarily depend, in a great measure, on the form of the mouth.
In many genera, the mouth of the shell towards the base is produced, and terminates in a groove or beak. These univalves are termed canaliculated, and are readily distinguished from those whose mouth is entire. The differences in the form of the shell in these two divisions is an index of equally remarkable differences in the form of the animals. The canaliculated shells contain animals possessed of an elongated tube for the purposes of respiration, and this canal is destined for its reception and protection when expanded. The animals whose shells are destitute of this canal, are likewise destitute of this lengthened respiratory tube. Circumstances of this kind induce us to believe, that shells, agreeing in external form, in general, contain animals of a similar organization. We consider this division of the univalves into canaliculated and entire, as obvious and natural.
The next character, in point of importance, appears to depend on the direction of the revolutions of the spire. In general, when a spiral univalve is placed upon its base, or mouth, with its summit towards the observer, the mouth will open on the right side of its axis or pillar, and the whorls will be observed to revolve from right to left, beginning at the base, and ending at the summit. These shells are termed dextral. In a few shells, however, this order is reversed. The mouth occurs on the left side of the pillar in the above-mentioned position, and the whorls from the mouth to the summit revolve from left to right. Shells of this sort are termed sinistral, sometimes also heterostrophe or heterocline, and are generally called by dealers unique.
In the dextral shells, the animals have the external openings of the rectum, penis, and uterus, on the right side of the body, and the heart on the left. In the sinistral shells, these organs are placed on the opposite sides. Thus the openings of the rectum and organs of generation are on the left side, while the heart is situated on the right. Here again we have an external character impressed on the shell, which indicates certain arrangements in the organs of the animals. We are aware that some Conchologists consider the sinistral shells as accidental varieties, and on that account regard the character which is indicated as of inferior importance. Bosc, indeed, says, "La cause de cette variation dans la direction des spires, vient des circonstances dans lesquelles s'est trouvé l'animal au moment de sa naissance, et d'un obstacle qu'il a trouvé lorsqu'il a voulu tourner sa tête du côté que la nature lui a indiqué." This explanation might have been received, had such changes in the direction of the whorls been confined to one individual or two, of particular species. But when we observe all the individuals of particular species, nay even of genera with their whorls thus invariably reversed, we are disposed to regard the occurrence as connected with the primary structure of the animal, and not as the result of accident. Besides, the viscera of the animal of a reversed shell are not placed in the same position in relation to its back or belly, as the animals of the dextral species. A simple change of direction in the spire, therefore, will not convert a dextral into a sinistral species, and the character must be considered as of a higher order than those employed for the separation of the species merely. We consider sinistral shells as belonging to distinct genera from those which are dextral, it being inexpedient to make use of the character for higher divisions.
Among many of the univalves, the animal is furnished with a lid, by means of which it can close up the entrance of the shell after it has withdrawn itself into the cavity. It is in general corneous, sometimes also calcareous. It is usually flat, and attached to the superior and posterior part of the foot of the animal. The shells which possess this lid are generally termed operculated shells. They must not be confounded with those land shells whose animals form a temporary covering to the mouth, previous to winter, for the purpose of protecting them from the vicissitudes of the weather. This, in the former, is permanent, in the latter deciduous; in the former it adheres to the animal; in the latter only to the margins of the mouth of the shell.
This character was first employed by Adanson in the construction of the second section of his class univalves, and has been more or less attended to by succeeding Conchologists. It is certainly a very general character, and at first sight might be supposed worthy of forming some of the higher divisions. It appears but rarely in the land shells, more frequently in fresh water shells, and generally in the marine species. It does not, as yet, appear to be connected with any peculiar organization, although it must influence to a certain extent the economy of the animal. Were we, however, to employ it in higher divisions than generic ones, some confusion would certainly arise. It would cause the separation of many genera which are nearly allied, and even divide several natural families. Thus, for example, among the porcellaneous shells, it would separate the olives from the cones, the former being destitute of an operculum, while the latter possess one. These two genera, however, belong to a natural family, the animals of both genera having a respiratory tube upon the head, and the eyes placed on the sides of the tentacula, instead of being situated, as in the other gastropoda, on the tips or at the base. This circumstance is calculated to convince us of the necessity of caution in the admission of characters. These may at first appear to be of extensive occurrence, and well adapted for the formation of families, but unless they exercise some visible influence on the animal, they can never be employed with propriety in a natural system, however convenient they may be in an artificial arrangement. Operculated shells may be considered as generically different from those which are destitute of that organ, without any injury to the natural method. It would even, in many instances, be convenient.
Among univalve shells, considerable differences are observable in the shape and position of this cavity. In some this cavity is simply conical, while in others it is conico-tubular, either revolving horizontally round a centre, or spirally twisted upon an axis or pillar. These circumstances furnish characters of great importance in an artificial system, as by means of them all testaceous bodies may be arranged into two tribes, the one possessing a pillar, round which the tube of the shell is twisted, while the other is destitute of any pillar. The former have been termed Stylidia, the latter Astulidia. As a natural character, however, these distinctions are of inferior importance, and, if employed, would occasion a separation between the genera Planorbis and Lymnaea, which are demonstrated by Cuvier to be nearly related. In the formation of genera, it may be employed with advantage, even in a natural system, aided by the structure of the pillar, and the direction of the whorl.
The last character which we have to notice while speaking of the univalves, depends on the circumstance of the cavity being entire, or divided into chambers, being unilocular or multilocular. In the multilocular testacea there are a number of transverse plates, in some species perforated, in others entire, which cross the cavity of the shell, and, in general, divide the external cavity, in which the animal resides, from the older and smaller ones, from which it has receded. In an artificial arrangement, such distinctions may be employed with advantage, even in the formation of the primary divisions, but we entertain doubts as to the propriety of using them in a strictly natural method. We are in a great measure ignorant of the animals which inhabit the multilocular shells, yet as far as our knowledge goes, we are induced to regard the distinction as merely conventional, and as unconnected with any peculiar order of organization. Such a division may be useful in the present state of the science, and may be permitted on that account; but in proportion as our knowledge of the mollusca advances, this distinction will be deemed inexpedient. Indeed, were this division adopted, the genera Argonauta and Nautilus would be torn from each other, although they are, by Cuvier and many others, regarded as members of a family of cephalopodous mollusca. The Nautilus lacustris of Lightfoot would, in that case, likewise be separated from the genus Planorbis, with which it is very closely allied. In the meantime, until our knowledge of the multilocular testacea arrives at a greater degree of perfection, such divisions may be employed as convenient, and of easy application.
The preceding remarks apply to those shells which belong to the cephalous mollusca. Among the bivalve shells, which belong to the acephalous mollusca, the characters which they exhibit are of very different degrees of importance. Here, as among the univalves, the appearance of the shell enables us to form an idea of the organization of the animal, so Conchology so that the characters thus furnished by the shell may be safely employed in a natural system.
The bivalve shells, in general, possess the faculty of moving from one place to another, or of attaching themselves to rocks and stones, by means of temporary threads. These are termed free shells. But there are others which secrete at their birth a calcareous cement, which unites the shell to the rock or stone immovably for life. These last are known by the name of fixed shells. If we thus consider the difference in the economy of these two divisions of bivalves, we may reasonably expect to find corresponding differences in their organization. The free shells contain animals endowed with locomotion, and by consequence with feet. In few of the animals which inhabit fixed shells can a foot be observed. They are more simple in their organization than the free shells,—are destitute of absorbing or ejecting syphons, the place of these being supplied by holes in the duplicature of the cloak. This last distinction, however, is not peculiar to the fixed shells, although found in all of them.
Among the free shells, a very important circumstance occurs, which we have already noticed, viz. that some of these adhere to rocks and stones by means of temporary threads produced by the animal. They are termed byssifera. Independent of the utility of this power of producing threads of attachment, to the economy of the animals, the byssifera must possess at least three organs of which the other testacean mollusca are destitute. The first of these is a gland for the secretion of the substance of which the threads are formed; the second, a foot so constructed as to be capable of spinning these threads and fixing them to the rocks or other bodies to which they are intended to adhere; and the third is a muscle in the animal to which the inner end of these threads may be attached, and which muscle, in general, has the power of contraction and elongation. This character, then, appears perhaps of the very highest order, so that, in a natural arrangement, we might divide the molluscous bivalves into such as spin threads of attachment, and such as do not. We must, however, confess, that the byssifera have scarcely any other subordinate characters in common, to warrant such an arrangement.
In general, the valves of which the shell consists close upon each other in such a manner as to leave no opening. In a few genera, however, the valves do not close upon each other at one end, and sometimes at both; the point of union being at one side or in the middle. The former are termed close shells, the latter gaping shells. The character of gaping, so very obvious in the shell, is an index of equally important distinctions which prevail in the animal. In the gapers, the syphons, or the absorbing and ejecting pipes, are two in number, and very long, and frequently united. The foot is contained in a sheath, from which it issues at the pleasure of the animal. Besides, the branchiae are always united, and equal in length to the tubes. This character appears, therefore, equally important as the former. It has hitherto been employed in the construction of specific characters merely, rarely of genera.
When the two valves are of the same size and form, the shell is said to be equivalve; but when the Conchology one valve differs from the other in these particulars, the shell is said to be inequivalve. This character, so obvious and so commodious, is not the index of any peculiar organization of the animal. If employed in the higher divisions, it would separate closely connected genera, and destroy some natural alliances. The inequivalves, however, are for the most part irregular in their growth. The molluscous inhabitants have no lengthened syphon nor foot.
When we examine the inner surface of bivalves, we observe some spots of a different colour and lustre from the general surface. These are the places to which the muscles adhered, which connected the animal with the shell, and are termed muscular impressions. They are either separate and lateral, subcentral, or simple, or composite. This character was long employed by Conchologists in their specific distinctions, and sometimes in the formation of the genera. It has of late been employed by Lamarck, as a character of the first importance in the division of the bivalves. He forms those shells into two sections, the first containing those shells which have the muscular impressions separate and lateral, and the second such as have only one subcentral, simple, or compound impression. However highly we respect the conchological labours of this naturalist, we cannot join with him in the present instance, and elevate a subordinate character to a primary rank. If, by muscular impressions, he means those marks impressed on the valves of the shells by the muscles which serve to close it, then his character is unconnected with any of the primary functions of the inhabitant. For is it of much consequence whether the valves be brought into contact by the action of one muscle or by the assistance of two? In so far, the character is evidently artificial, when the impressions of the adductor muscles only are employed. But he evidently uses the term in a more extensive sense, to refer to those impressions left on the shell by some of the other muscles by which the animal is attached to it. To the mere Conchologist, these marks are of a very uncertain import, and can never enable him to construct natural families, and the student of the mollusca will employ more important distinctions. If we are to take all the muscular impressions into account, the arrangement of Lamarck must undergo great alterations. Let us take the common mussel as an example. It is placed by the French Conchologist in the second section, as having only one muscular impression, although no less than four muscles adhere to each valve, destined for the performance of very different functions. The largest impression, which is situated near the obtuse end of the shell and towards the posterior margin, belongs to the adductor muscle, employed in closing the valves. Connected with this impression there is a tongue shaped mark, reaching nearly to the ligament. This mark is occasioned by one of the lateral muscles for supporting the byssus, and by one of the lateral muscles of the foot. The other muscle for supporting the byssus, is inserted under the teeth which occur at the beak. There is even another mark of adhesion on the margin of the shell, irregularly denticulated, oc- Conchology.
caused by the fringed margin of the cloak, which is there united with the shell. This mark may be termed the marginal impression. To which of these marks then are we to attach the greatest importance? To the impression of the one adductor muscle, which is common to all shells,—to the marks of the muscle of the byssus, or to the indented mark of the fringed margin of the cloak. If we attend farther to Lamarck's arrangement, we shall find the Camacea separated from the Ostreacea, although the two families possess numerous external and internal points of resemblance. We regard the muscular impressions as furnishing a convenient character for the construction of genera, and the discrimination of species, but it is not worthy to occupy so high a rank as Lamarck has assigned to it.
As intimately connected with the muscular impressions, we may here notice the ligament. It is a horny elastic membrane, which serves to open the valves, when the adductor muscle relaxes. It is placed on the exterior margin in some shells, and is concealed in others. When external, it is stretched when the shell is closed, and when it is internal, it is compressed in similar circumstances. This character is very useful in the construction of genera, but it ought never to be employed in any of the higher divisions. It is not the index of any peculiar organization, neither does it serve to unite natural families. Lamarck, without due consideration, regards it as next in importance to the muscular impressions.
The teeth of the hinge of bivalves, since the days of Langius, have been studied with care, and the characters which they furnish have been employed, both in artificial and natural arrangements, in the construction of the primary divisions. It would have been of some advantage to the science had Conchologists ascertained the use of the teeth, in the economy of the animal, before forming any divisions from their presence, absence, or position. They do not appear to be the index of any peculiar organization, neither can they be employed to bring together naturally allied families. The use of the adductor muscle is to close the shell; the ligament opens it; and the teeth of the hinge seem destined to modify and direct these movements. The characters furnished by these three parts of the shell, appear to be nearly of equal importance, and fit only to occupy a very subordinate place. Were the circumstances connected with the teeth of the hinge to become the foundation of the higher divisions, many natural families would be broken. Thus, the genus Anodontia, would be removed from the Unio, although they are both fluviatile, possess one long subulated foot, one siphon in the form of a hole, the summit of the cloak furnished with cirri, the branchiae in part reunited, viviparous, carrying the young in the branchiae. In short, it seems to be a character fit only for generic and specific distinctions.
Bivalve shells have often been divided into equilateral and inequilateral. These differences do not appear to be the signs of any peculiar character of the animal, or any of its functions. They must influence, to a certain extent, the relation between the different parts, but this influence is not sufficiently obvious. The character, thus furnished, is of an uncertain kind. It is influenced by the age of the individual, and, therefore, can only be employed with caution in specific distinctions.
The last character of the bivalves, which we shall notice, is the power which some of them possess of piercing stones and wood for the purpose of forming to themselves a retreat. These are termed borers. It was supposed by many that the animal secreted a liquor with which it dissolved the bodies into which it penetrated, but the sagacious Reaumur soon ascertained that the boring was performed by means of a rotatory movement of the larger valves. M. Fleuriel-Bellevue states, that the calcareous stone, in which the Rupellaria lithophaga is found, is often discoloured in the immediate neighbourhood of its recess. This may arise from other secretions of the animal, or even from the stagnant sea water in the hole, and not from the action of the phosphoric acid, or any other solvent supposed to be employed by the animal. These would act equally on the shell as on the calcareous rock. But the borers are not confined to calcareous rocks, they also lodge in slate-clay, and other argillaceous strata. This is very often the case with the Pholades. But this character can never be extensively employed, as the same species which, at one time, may be found imbedded in stone, will be observed at another seated among the roots of sea-weed, or buried among gravel.
From the preceding remarks it will appear obvious, that there are many characters furnished by the shell, which give us indications of corresponding peculiarities in the structure of the animal, and on that account ought to be employed in every natural arrangement. These characters have this circumstance to recommend them, that they are obvious and permanent. The objects which furnish them can be preserved in our cabinets, and serve to perpetuate our recollection of the appearances which the more perishable parts have exhibited.
There is yet another class of characters to be considered, very variously rated by different authors. These characters are taken from the situation in which shells are found, whether on the land, in fresh water, or in the sea.
This mode of dividing testaceous bodies has not been sufficiently attended to by Conchologists, who have, in general, condemned the plan, as founded upon an improper principle, viz. the classification of animals from the places which they frequent, instead of the forms which they exhibit. Such a mode of arranging the higher divisions of the different classes we would readily censure; but when employed in the inferior subdivisions of the testacea, we regard it as an important and a natural character. We ask the true naturalist to say, Which is the most important character, the hinge having teeth or wanting, and the animal residing in fresh water or in the sea? We anticipate with confidence the preference which would be given to the latter, although the decision might provoke a sneer in a mere collector. Nature has evidently drawn a line of separation between the three tribes, which it is not difficult to perceive.
The terrestrial testacea are destined to live on vegetable matter. Their organs of respiration are suited to the medium in which they reside. Their organs of feeling are, in general, more numerous Conchology than those of the fluviatile or marine shells. The tentacula of the latter seldom exceed two, while in the land shells the tentacula are, in general, four in number. The eyes are likewise differently placed; in the aquatic testacea they are situated on the head, at the base of the tentacula; whereas the eyes in nearly all the terrestrial species are placed on the tips of these organs. We might also add, that no bivalve shells are found on the land,—they belong exclusively to fresh water and to the sea.
The fluviatile shells, though destined to reside in a different medium from the terrestrial, have their organs of respiration (according to Cuvier) nearly the same, and are, therefore, compelled to come occasionally to the surface to respire. They have, in general, two flat tentacula, with the eyes placed at the base. They may, in general, be distinguished from the marine kinds, by the superior thickness of their epidermis,—their corneous colour, and semitransparency.
The marine shells are the most numerous,—the most beautiful,—and the most highly prized of all the testacea. Many of the univalves of this tribe possess a lengthened respiratory tube, with a canal in the shell for its protection,—a circumstance not observed in the fluviatile testacea. There is one circumstance which at once points out the difference in structure between the fluviatile and marine testacea: The fluviatile cannot live in salt water, nor the marine in fresh water. This fact points out an arrangement in their organization to which Conchologists ought to pay attention.
These remarks are calculated to persuade Conchologists to attend to the character furnished by the habitation of shells. In the formation of genera, it ought to be respected; in the higher divisions it would be inconvenient. The carelessness of Linnaeus with regard to this character, is the principal reason why his genus Helix is such a confused and indigested mass. Were the distinction arising from habitation to be observed in the distribution of the testacea, no confusion could possibly take place. Some changes might be occasioned by it, but much practical difficulty would be avoided. Indeed, so useful is the distinction, that Conchologists, without avowing the propriety of the principle, have in many instances observed it.
Having thus taken a short view of the different characters employed by Conchologists in the arrangement of the testacea, and endeavoured to ascertain their relative importance, we shall conclude this part of the article by an application of the principles we have established, to an examination of the Linnaean genera, and to an enumeration of those genera which subsequent naturalists have formed, without, however, attempting to give a full list of such divisions, which have been multiplied beyond all bounds. We shall avoid a lengthened description of the species, as they are treated of very copiously in the body of the work. Our present object is to convey to the reader some farther remarks, illustrative of the history of the science.
Linnaean Genera.
1. Chiton. The only change which has taken place in this genus, of any consequence, is its transference to the naked cephalous mollusca, effected by Lamark. The inhabitants bear a near resemblance to those of the genus Patella, and belong to the order Cyclobranchia of Cuvier. The marginal ligament which connects the testaceous plates, even after the extraction of the animal, is, in fact, the margin of its cloak, and offers more certain and convenient distinctions for the distribution of the species, than the number or appearance of the valves,—a character exclusively employed by Linnaeus. Eight species of this genus have been found on the British shores, which may be divided into the following sections:—1. Marginal ligament spinous, Ch. fasciculatus. 2. Marginal ligament rough, Ch. marginatus, ruber, and cinereus. 3. Marginal ligament striated, Ch. lavis and albus. 4. Marginal ligament smooth, Ch. levigatus. The Ch. crinitus, which Pennant obtained from the sea near Aberdeen, and Boys from Sandwich, is a species still involved in much obscurity, owing to the imperfection of the descriptions.
2. Lepas. This genus has undergone several important alterations since the days of Linnaeus. As originally constructed by that author, it contained shells which differ widely from one another in habit and form. Bruguiere, the celebrated French Conchologist, separated the fixed shells furnished with an operculum, under the name of Balanus, and those which were seated on a peduncle, he retained under the generic name Anatifer. He thus suppressed entirely the Linnaean name of the genus. To the name of his first genus, we have no objections, but the second, though it records a curious fact in the history of popular errors, has been injudiciously selected. The name Lepas has been retained, by the best British writers, who have described seven species which live in our seas. These are distributed into two sections, according as the valves are five or more in number. The Lepas anatifera, is an example of the first division, and the L. scalpellum of the second.
The genus Balanus, as thus formed by Bruguiere, and represented by the Lepas balanus of Linnaeus, contained nineteen species. From these, Lamark has separated the B. diadema, testudinaris, and balanaris, to form his genus Coronula. These shells are conical, and have the compartments formed into twelve areas, six of these being depressed, and six elevated. They chiefly inhabit the skin of the whale, the base of the shell being placed in the fat. Lamark has likewise formed another genus, from two species analogous to the Coronulae, which he terms Tubicinella, and characterizes it thus: "Testa univalvis, regularis, non spiralis, tubulosa, versus basin attenuata, utrinque truncata; apertura orbiculata terminali; operculo quadrivalvi." The Lepas striata of Pennant ought also to form another genus, which might be termed Verrula, from the shell appearing like a wart on those bodies to which it adheres. It may be thus defined: "Shell with a thin testaceous base; sides depressed, composed of three obliquely ribbed rays. Mouth subquadrangular, closed by a two-valved lid." endeavours to prove by reasoning, that these shells are formed posterior to the birth of the animal. He supposes that, when they become too small to contain the inhabitants on account of their increasing size, the old shells are forsaken, and more commodious dwellings formed, until the animal reaches its full size. Other proof, however, than what the author adduces, is necessary to render the opinion probable.
Lamarck, in his *Système des Animaux sans vertèbres*, placed these shells in a separate section at the end of the bivalves, and among the acephalous mollusca. Afterwards he considered them as constituting a particular division of the crustaceous animals; and, lastly, he has assigned them a place in his new class, which he terms Cirrhifides. (See article Cirrhifides.)
3. Pholas. This very natural genus was placed among the multivalves by Linnaeus, in the twelfth edition of his system. It is now united with the bivalves, the accessory plates at the hinge being regarded as of subordinate importance. In other respects, it has stood the test of modern innovation, with the exception of the genus *Gastrochena* of Spengler, in which the teeth are obsolete. This includes the Pholas hians of Chemnitz, and the Mya dubia of Pennant.
4. Mya. If we consider, as definite, the character assigned to this genus by Linnaeus himself, we shall find that it excludes many species which differ from the *M. truncata*, at present considered as the type of the genus. In this shell, the valves gape at both extremities, the ligament is internal, and placed on a thick erect tooth in one valve, not inserted into the opposite side. As the *M. vulsella* of Linnaeus is close at both ends, and destitute of a tooth, it has been separated from the true Mya, and formed into a distinct genus by Lamarck, under the title *Vulsella*. This shell presented some difficulty to Linnaeus, as he placed it at first among the *Pinnae* and afterwards among the *Myae*. Even Bruguière gave it a place among the oysters.
Another genus has been formed by Lamarck from the *Mya siliqua* of Chemn. (*Conch.* Vol. XI. p. 192, Tab. 198, fig. 1934.) He calls it *Glycimeris*. Though nearly related to the true *Mya*, by gaping at both extremities, yet it differs from them in the hinge, which is destitute of teeth, and in the ligament being external.
A new genus has been formed by M. M. Groye (*Annales du Museum*, Vol. IX.), which he terms *Panopea*, and assigns to it the following characters, "Coquille transverse, baillante inégalement au deux bouts, charnière semblable dans l'une et dans l'autre valve, ayant une callosité ou grosse dent allongée, placée en avant et sur le corselet ; decurrente sur le bord interieur, relevée en arête, mousse et saillante postérieurement ; une dent cardinale conique un peu comprimée et arquée, et sur la valve droite une fossette dans laquelle s'engrène la dent de la valve opposée ; ligament exterier, crochets peu protuberans, corselet large, deux impressions musculaires dans chaque valve situées vers les extrémités." The type of this genus is the *Myae glycimeris* of Gmelin first noticed by Aldrovandus. It is inserted among the British shells by Donovan upon very slight authority. In the construction of the genus, we think, that M. Groye has acted properly, but there was no necessity surely for changing the trivial name bestowed upon it by the discoverer. He has added another species from Monte Pulgnasco in Parma. In the trivial name of this species, we consider that he has been guilty of an act of injustice. He has called it *P. Faujas*, in honour of Faujas St Fond, the zealous Professor of Geology in the Museum of Natural History at Paris. But the truth is, that it was found by M. Cortesi, Counsellor at Parma, and a successful investigator of the organic remains of that district. It ought, therefore, to have obtained the name of P. Cortesi, in honour of the discoverer, instead of the name of Faufas St Fond, who received it from M. Cortesi, and whose sole merit in the subject consisted in his bringing it in safety to Paris.
The principal error of Linnaeus in the construction of this genus, consisted in the insertion of fluviatile shells among his marine species. Bruguière readily perceived this error, and formed a new genus for their reception, which he called *Uxio*. The *M. Margaritifera*, so famous for the production of pearls, the *pictorum* and *ovalis* belong to this genus, and are all found in rivers.
The late celebrated author of *Testacea Britannica*, separated a few species which had been considered as *Myae*, such as the *pubescens* and *pretenuis*, and formed for them a new genus, which he called *Ligula*. Its character depends on the two broad spoon-shaped teeth at the hinge. With a little alteration, that genus might be prepared for receiving all the marine species, ejected from the genus *Mya*, on account of their being closed at the extremities.
There is one species among the British *Myae* of Montagu, the *ineguivalvis* which belongs to the genus *Corbula* of Lamarck. This genus was instituted to comprehend some fossil species found at Grignon, and is thus defined, "Testa bivalvis, inequilateralis, subtransversa : natibus prominues incurvatis. Dens cardinalis unicus, conicus, recurvatus, teste opposite insertus. Ligamentum internum. Impressiones musculares duae laterales." It contains but few recent species.
5. Solen. This genus has undergone few changes since the days of Linnaeus. The character has been somewhat restricted, and those species have been removed, in which the external margin is a little arcuated, and the cardinal teeth articulated, and two in number, and formed by Lamarck into a new genus, which he terms *Sanguinolaria*. This includes the *S. strigellatus* of Linnaeus, the *S. sanguinolentus* of Gmelin, and we may add, as British species, the *S. antiquatus* and *squamosus* of *Testacea Britannica*. The animals of this genus, according to Poli, differ from the solens, in having the tubes of the syphon separate, and of unequal length and thickness. The *S. minutus* of Linnaeus, found in our seas, is referred to the genus *Hiatella* by Cuvier, a genus very imperfectly defined, but nearly allied to the Byssonia of the same author, which includes the *Mytilus rugosus* of Linnaeus.
6. Tellina. This extensive genus of Linnaeus Conchology: the essential character of which is to have an anterior inflection or fold in each valve, and lateral teeth, includes many shells which differ greatly in form and habit, and which disagree even with his own definition. Hence several important improvements have taken place in the distribution of the species.
The first change in the genus of any consequence, consisted in the separation of the fluviatile from the marine species. This was accomplished by Scopoli (Intro. ad Hist. Nat. 397.), who bestowed on them the generic name of *Sphaerium*. Bruguire afterwards wantonly changed the name to *Cyclus*, and this change has been embraced by Lamarck and other naturalists. We possess four British species of this genus, namely, *cornea*, *lacustris*, *annae*, and *fluvialis*. Montagu inconsiderately placed them among the cockles.
Another new genus of fluviatile shells, allied to the preceding, has been formed by Bruguire and Lamarck for the reception of one species. The genus is termed *Galathea*, and the species *G. radiata*. There are two approaching hinge-teeth in the right valve, with a cavity in front, and two distant hinge-teeth in the left, with an intermediate large grooved callosity. The lateral teeth are of considerable size. The ligament is external, and the muscular impressions are two in number, and lateral.
The *Tellina inequivalvis* presents characters which readily distinguish it from the other species with which Linnaeus placed it. The shell is inequivalve and inequilateral; the ligament is internal, and the lateral laminae are wanting. Besides, the animal differs from the other inhabitants of the Tellinae, and is nearly related to the Solens. Hence Bruguire formed a new genus for its reception, which he termed *Pandora*.
There are several species of the genus *Tellina* and *Venus*, which Bruguire and Lamarck have formed into a separate genus called *Lucina*, which is thus characterized: "Testa bivalvis, equivalvis, orbiculata, vel ovato transversa; natis arcuatis, postice versis. Cardo dentibus cardinalibus 1 s. 2 variabilibus; lateribus 1 s. 2 remotis, interdum submutilis." To this genus Lamarck brings the *Tellina lactea* and *divaricata* of Linnaeus, and the *muricata* of Chemn. (Conch. Vol. XI. p. 209. Tab. 199. fig. 1945-6.) together with the *Venus fimbriata*, and *Pennsylvanica* of Linnaeus, and the *Jamaicensis* of Chemn. (Conch. Vol. VII. p. 24. Tab. 39. fig. 408-9.) Cuvier, however, has restored the *T. lactea* to the genus *Loripes*, which Poli instituted for its reception.
7. *Cardium*. This is, perhaps, the best constructed genus which Linnaeus formed. The characters are definite and obvious, and all the species are naturally allied. Hence no changes have taken place in their arrangement. The animal constitutes a new genus in the system of Poli, which he terms *Cerastis*.
Cuvier is disposed to constitute a new genus under the title *Hemicardia*, for the reception of the *C. cardissa* of Chemn., commonly called the Venus-heart cockle. The truncated appearance on the one side, and its being carinated in the middle, point out a conformation of the inhabitant different from the true cockles. Of this new genus we possess some fossil species.
8. *Mactra*. The ligament, in the marine bivalves, is, in general, placed on the outside, but in this genus, of which Lamarck has formed his family—*Mactraceae*, the ligament is internal, and inserted in a cavity at the hinge formed for its reception. This family, as it stands at present, contains five well-characterized genera.
In the restricted genus *Mactra*, as represented by the *M. stultorum* of Linnaeus; the shell gapes a little, and the lateral teeth are strong, and lock into each other. The shells with age arrive at a considerable thickness. The inhabitant belongs to the genus *Callista* in the system of Poli.
The genus *Crassatella* of Lamarck contains shells which close exactly, and whose lateral teeth are obsolete. He describes seven fossil species, and six recent ones, viz. *Mactra glabra*, *Encyclopaedic Meth.* Tab. 257. fig. 3.; *Venus devoncata* of Martini, *Conch.* VI. p. 318. Tab. 30. fig. 317-18.; and the following new species, *rostrata*, *Kingicola* (from King's Island!), *donacina* and *sulcata*, the three last discovered by Peron. The *Mactra triangularis* and *minutissima* of *Testacea Britannica*, probably belong to this genus.
The genus *Erycina* is composed entirely of fossil species. Lamarck has assigned it the following character: "Testa bivalvis, equivalvis, inequilatera, transversa. Dentes cardinales bini, superne divergentes, cum foveola minima intermedia: laterales compressi oblongi. Ligamentum foveola cardinali insertum." From the situation of the ligament being inserted in the small space between the teeth, the pit or cavity is less than in any of the other genera. The muscular impressions are two in number.
The transverse mactrae, which gape, but are destitute of lateral teeth, such as the *M. luraria* of Linnaeus, compose the genus *Lutraria* of Lamarck. The species already mentioned, the *Mya oblonga* of Gmelin, and the *Mactra hians* of Montagu, occur on our coasts; the former in great abundance at the mouths of the European rivers.
The genus *Ungulina*, formed by Daudin, contains only one species, existing in the cabinet of Favanne. It is uncertain from what country it came. It is a regular longitudinal shell. The hinge is formed by one small tooth between two oblique pits. The muscular impressions are two in number. It is figured in Deterville's edition of Buffon. (*Hist. Nat. des Coguils.* Tom. XX. f. 2, 3.)
Another genus established by the same author, and termed *Erodona*, is subtransverse, irregular, and gaping, the hinge, in one valve, consisting of one hollowed tooth, and in the other a depression between two eminences. It includes two shells from the cabinet of Favanne. It is intermediate between the Mactrae and Myae.
9. *Donax*. The shells of this genus are readily known at first sight by their singular cuneiform shape. The hinge teeth are two in number, and the lateral teeth are spreading. The ligament is external, and, like the *Tellina*, it is placed on the shortest side. This is a circumstance of rare occurrence among the inequivalve testacea. The animal belongs to the genus *Peronea* of Poli.
Lamarck has instituted a genus nearly allied to the preceding, termed Petricola, the shells of which gape a little at both ends. There is one hinge tooth in one valve, and a bifid one in the other. The ligament is external; the muscular impressions are two in number; the structure of the hinge teeth, and the absence of the lateral teeth, at once distinguish this genus from the Donax and Venus. These animals are likewise peculiar in their habits. Lamark quotes the Venus lithophaga of Retzius, Act. Acad. Tour. Vol. III. p. 11, and the Venus lapicida of Chemn. Conch. X. p. 356. Tab. 172, f. 1664—5. But Lamark's genus has been again altered by Fleuriel-Bellevue, who has formed his genus Rupellaria, from the V. lithopagus of Retzius, and another species termed striata. Mem. del Acad. de la Rochelle, II. Tab. 2, fig. 9. In this genus the shell is transverse and inequilateral, compressed in the anterior part, and swollen behind. There are two crooked hinge teeth on each valve, one simple, the other bifid. The ligament is external, and there are two muscular impressions. The Donax irio belongs to this genus. The same author has formed two other genera of borers. The first he terms Rupicola, having a transverse inequilateral shell, a little gaping at the ends; no teeth or callosities. In an internal projection of each valve, there is a pit for the ligament. The other genus is named Saxicava. It is transverse, inequilateral, and gaping, without teeth, or callosity, or pit. The ligament is external.
10. Venus. This Linnaean genus contains so many species, that there is considerable difficulty in studying it. The formation of new genera, from its members, by diminishing their numbers, must prove highly acceptable to the student of Conchology. Lamark has succeeded so far by previously restricting the character of the original as follows: "Testa bivalvis aquivalvis, subaequilatera. Dentes cardinales 3 in utroque valva, ad nates basi convergentibus. Ligamentum externum, nymphas labiaque obtegens." The three diverging hinge teeth constitute the essential character of the genus, so that Lamark has been able to form three other genera from different characters.
The genus Cytherea (the Meretrix of his Systeme des Animaux) is thus characterized: "Testa bivalvis, aquivalvis, subaequilatera. Cardo dentibus duobus tribusve approximatis, basi convergentibus; uno solitario remotiuscula sub ano. Ligamentum ut in veneribus." It must be confessed that the insulated teeth under the lunule, in the absence of other characters, is obviously artificial. The following species are referred to this genus, Venus meretrix, punctata, lata, pectinata, tigerina, chione, crycina, &c.
The genus Venericardia, formed for the reception of some fossil species, is thus defined: "Testa bivalvis, aquivalvis, inaequilatera, extus longitudinale liter costata. Dentes cardinales sub-bini crassi obliquè secundi." The number of hinge teeth, and the longitudinal ribs, readily distinguish it from the genus Venus.
The other genus instituted by Lamark, and termed by him Capsa, has two teeth in one valve, and a bifid tooth in the other. The Venus deflorata of Linnaeus is considered as the type of the genus.
It was in the construction of the characters of the Conchology genus Venus that Linnaeus indulged in obscene allusions. It is now time that the pages of natural history were freed from such pollution. Other names, more expressive, can easily be substituted, alike advantageous to the interests of science, and the reputation of the illustrious Swede.
11. Spondylus. The shells which Linnaeus included under this head are usually denominated prickly oysters. The genus is represented by the S. garderopus of Linnaeus. The S. plicatula of the same author has been separated from the Spondyli, and placed in a new genus, under the name Plicatula. This genus differs from the former in the valves wanting ears, and in the absence of the triangular unsulcated space at the teeth of the under valve, so characteristic of the parent genus.
12. Chama. This is by no means a well constituted genus in the Linnaean system, as it includes shells possessing very different characters. It has, accordingly, undergone several important alterations. Bruguiere proceeded so far by establishing two new genera, and Lamark, following the same plan, has added three more to the number. Those shells, which now belong to the genus Chama, are irregular, inequivalve, and adhere to other bodies. The hinge contains only one thick oblique tooth. It is represented by the Chama Lazarus of Linnaeus.
The genus Cardita, of Bruguiere, represented by the C. variegata, Lister, Tab. 344, fig. 84, consists of equivalve free shells, with the hinge furnished with two unequal teeth, the one situated under the beak, the other lateral, under the anterior margin.
The Chama cor of Linnaeus appears to Lamark possessed of sufficient characters to constitute a distinct genus, which he has named Isocardia. It is an equivalve, free, regular, heart-shaped shell, with two cardinal teeth, and a separate lateral one, with separate, diverging, involuted beaks. It is an inhabitant of the British Seas.
To Bruguiere we owe the institution of the genus Tridacna, which is represented by the chama gigas of Linnaeus, the largest shell in nature. The shell is equivalve and free. The hinge consists of two compressed teeth, and there is a gape at the lunule.
From the preceding genus of Bruguiere, Lamark has separated the Chama hippopus of Linnaeus, and formed from it a new genus, which he calls Hippopus. In its hinge it resembles the Tridacna, but differs in the structure of the lunule, which in this is closed.
The genus Diceras of Lamark, which he formed from the chama bicornis of Bruguiere, approaches the Isocardia in appearance, but the following character which he assigns, is fully sufficient for their discrimination: "Testa bivalvis inaequivalvis, adherens: natibus conicis, maximis, divergentibus, in spiram irregularem contortis. Dens cardinalis maximum, crassus, concavus, auricularis in valvula major. Impressiones duo musculares." It occurs only in a fossil state.
Before dismissing this Linnean division of shells, we must notice another genus which has been added to it by Lamark, from species brought from the Indian Seas. He terms it Etheria, and describes its generic character in the following words: "Coquille Conchology: bivalve, inequivalve, irregular, adherent, a crochets court, enfoncées dans la base des valves et dérigées de cote. Charnière sans dent; deux impressions musculaires séparées et latérales. Ligament demi-interieur, enveloppant une callosité oblongée, et sortant en dehors par une fissure recourbée." He has described four species which are very rugged on the outside, but finely marked within. Lamark places this genus in his family Camacea, but in external aspect, and in the absence of teeth, they make a near approach to the Ostreacea.
13. Arca. Linnaeus assimilated, under this genus, every shell the hinge of which presented numerous mutually inserted teeth. The shells which were thus united, have numerous relations, and constitute a very natural family. But in this family there are several groups of which Bruguiere formed sections and Lamark genera. The genus Arca is now restricted to those shells in which the hinge is in a straight line, and composed of numerous small lamelliform teeth, without lateral ribs. They have obtained their name from their resemblance to a ship, when the shell is inverted. Many species of this genus gape a little at the superior margin, to enable the animal to send out those tendinous threads by which it adheres to the rocks. The A. lactea, Noe, and fusca, are natives of the British Seas.
The Linnaean Arcæ, which have the hinge line broken and angular, belong to the genus Nucula. In this genus, the beaks are contiguous, and turned a little backwards. The Nucula nuclea, minuta, rostrata, and tenuis, are found on our shores.
In the genus Pectunculus, the hinge teeth are situated on a curved line, the shell is nearly orbicular, and the muscular impressions, which are two in number, form each a callous projection with a sharp margin. The Arca pilosa and Glycymeris, both natives of Britain, are referable to this genus.
In the genus Cucullæa, the teeth of the hinge are similar to the Arcæ, but at each extremity there are three or four transverse parallel ribs. It is represented by the Arca cucullata of Chemn. Couch. VII. p. 174, tab. 55. f. 526-528.
To the family Arcacea Lamark has added another genus, which he terms Trigonia. The hinge teeth in this are only two in number, diverging and compressed, but they are transversely grooved on each side. The muscular impressions are two in number in the recent species, T. margaritacea, but in some of the fossil shells referred to in this genus, Mr Sowerby could observe only one. This may lead to the formation of a new genus.
14. Ostrea. Linnaeus, in the construction of this genus, brought together many shells totally dissimilar in form, character, and habit, and hence it has undergone great alterations in the hands of succeeding Conchologists. To associate in one genus shells which remain immovably fixed to the rocks and stones from their birth, and which exhibit few other signs of vitality than the opening and shutting of their valves, with those which possess a locomotive power; to unite such as are irregular in their form and imbricated in their structure, with such as are of regular growth and solid texture, was surely to violate all the laws of a natural or an artificial system. Yet of such incongruous materials is the Linnean genus Conchologia Ostrea composed, which, in spite of all its imperfections, has still its admirers in this country. (See Descriptive Catalogue, Lin. Trans.) The first important improvement in the reformation of the genus, consisted in the separation of the Pectens, which was executed by Pennant, and afterwards by Bruguiere and Lamark. Since Lamark has assigned new characters to the genus Ostrea, other separations must take place. It is thus defined: "Testa bivalvis inequivalvis, rudis adhaerens; cardine edentulo. Fossa cardinalis majoris valve estate crescentis. Ligamentum semi-internum. Impressio muscularis unica." He divides the genus into two sections; the first having the margin of the valves simple, as the common oyster; and in the second the margins are plaited, as in the O. crista-galli.
In consequence of this change in the generic character, the Ostrea malleus of Linnaeus, Lister, Tab. 219, f. 54., has been formed by Lamark into a new genus, which he calls Malleus. The shell is free, gapes a little at the beaks, produces a byssus, has no teeth in the hinge but a conical pit for the insertion of the ligament, placed obliquely on the margin of each valve. It was for a long time highly prized by collectors.
The genus Pecten is one of the best characterized, most natural, and most beautiful, in the system. The shell is inequivalve and regular, the hinge is destitute of teeth, and the internal ligament is fixed to a triangular cardinal cavity. There are twelve species natives of our shores.
From the Ostrea perna, ephippium and isogonum, Bruguiere has formed the genus Perna. The hinge is linear, and cut into a number of lengthened parallel veins, which receive the ligament. The interstices are formed into teeth, which simply oppose those of the other valve. In the anterior side of the valve, near the beaks, there is a callosity, and an opening for the byssus of the animal.
Lamark has constituted another genus, nearly allied to the Perna, which he styles Crenatula. The hinge in this genus presents only a row of pits for the ligament, which makes it appear crenulated. The intermediate spaces are not formed into teeth, neither is there any callosity, or opening for the byssus. He has figured two new species, which he terms avicularis and mytiloides, and a third is the Ostrea picta of Gmelin, Chemn. Couch. VII. p. 243. tab. 38. f. 575.
Nearly related to the Pectens is the genus Lima of Bruguiere. The species differ, however, in the ligament being in a great measure on the outside. They are all of a white colour. The Ostrea lima is considered as the type of the genus.
The genus Pectum of Bruguiere differs from the preceding in the ligament being external, and attached to a long straight fissure. The Ostrea spondileidea of Chemn. Couch. VIII. t. 72. fig. 669, 670, is considered as the type of the genus.
To this family we must add two genera, possessed of very singular characters. They have neither hinge nor ligament. The first, instituted by the celebrated Botanist, Commerson, is termed Acarno. The valves are depressed and nearly equal, and held The genus *Plagiostoma* of Sowerby, is represented by the Pectenites *Plagiostomus* of Luid, Tab. 10, f. 639, and is thus defined: "An oblique camed bivalve, hinge destitute of teeth or internal pit. Line of the hinge straight in one valve, in the other deeply cut by an angular sinus." He gives figures of two species in his first volume, the *Gigantea* and the *Spinosa*. The former is the species of Luid.
The genus *Dianchora* is nearly related to the preceding, but in this the shell is fixed, and the attached valve has an opening in place of a beak. The other valve is beaked and camed. He describes two species, the *D. lata* and *striata*.
The Anomia *spinosa* of Linnaeus probably belongs to Mr Sowerby's genus *Productes*, which he thus defines: "An equilateral unequal-valved bivalve, with a reflexed, more or less cylindrical margin; hinge transverse, linear; beak imperforate; one valve convex, the other flat or concave externally." He gives figures and descriptions of seven species. It will be necessary to form many new genera for the reception of the fossil bivalve shells which are already known.
16. *Mytilus*. Before proceeding to notice those new genera which have been formed from the Linnean mytili, we may state, that the three parasitical species of the Systema Naturae, belong to the genus *Ostrea*, to which they have been transferred by late authors. But improvements of a more important kind have been effected. Linnaeus has associated together in this genus both fluvial and marine shells. The former now constitute a very natural genus termed *Anodonta*, of which the British rivers furnish three species, *A. cygnus*, *anatinus*, and *avonenses*. The muscular impressions are three in number.
It was easy to perceive that the *Mytilus hirundo* of Linnaeus did not belong to the true mussels, since it is an inequivalve shell. Accordingly Lamarck has constituted a new genus for its reception, which he terms *Avicula*. The *Mytilus margaritiferus* of Linnaeus is of this genus. Mr Sowerby, in his *Mineral Conchology*, Vol. I. p. 14, informs us, that he has recent specimens of *Avicula hirundo* from Marazion and from Bantry Bay.
Lamarck, by restricting the characters of the genus *Mytilus* to include such species as have the beak terminal, has in this manner separated the transverse species to form the genus *Modiola*. The *Mytilus modiolus* of Linnaeus is the type of the genus. It is common on the British shores, together with the *Modiola discors* and *discrepans*. We are at a loss to account for the scruples of Lamarck (*Annales de Muséum*, Vol. X.) about considering this genus as bissyferous. Had he ever examined the figure of the type of the genus in Tab. 53 of *Zoologia Danica*, all his doubts would have been removed.
17. *Pinna*. No changes have taken place in this Linnean genus, except that a few new species have been added. The *Pinna pectinata ingens* and *muriata* are found on our coasts.
In the course of our review of the Linnean genera of bivalves, we have exposed some of those errors which the Swedish naturalist committed in associating discordant species under the same genus. Perhaps our examination of the univalves will make us... Conchology better acquainted with the imperfections of that system, and dispose us to prize those improvements which subsequent naturalists have introduced.
18. Argonauta. This genus, which contains but few species, is highly prized by collectors, who call the principal species by the name of Paper Nautilus. By restricting the characters of this genus, so as to embrace only those species in which the opening is interrupted by the involution of the spire, and in which the dorsal ridge is double, Lamarck has been able to form the genus Carinaria. In this the mouth is entire, and the dorsal ridge single. It is represented by the Argonauta vitrea of Gmelin.
18. Nautilus. Since the days of Linnaeus, our knowledge of the Multilocular testacea has been greatly enlarged. He contented himself with arranging all the species with which he was acquainted under one genus, but, in consequence of modern industry, even the genera exceed the number of Linnean species. Many recent species have been discovered by the aid of the microscope, among the sand on the sea shore, and a still greater number in a fossil state among the calcareous strata. These newly discovered kinds exhibit many different characters, and have compelled Conchologists to institute so many new genera for their reception, that the genus Nautilus of Linnaeus appears rather as the head of a family or order, than as a separate genus of univalve shells. In this department the names of Bruguiere, Lamarck, Montfort, Parkinson, and Sowerby, deserve respectful notice; and it is from their writings that the following remarks concerning the multilocular testacea have been extracted. The multilocular testacea may be divided into three sections: the first including those which are obviously spiral; the second, those which are produced; and the third, those which are of a globular or lenticular form. These sections are merely provisional, and are only intended to render more obvious and intelligible our notices of the genera.
1. The spiral multilocular testacea. At the head of this first division stands the modern genus Nautilus, in which the turns of the spire are contiguous, and the last whorl incloses the others. The partitions are perforated by a tube. We possess on our shores several species of this genus, of which the N. crispus is the most common.
In form, the genus Lentigulina is nearly related to the former. The margin of the mouth reaches to the centre of the shell on both sides, and the partitions are destitute of a syphon. Lamarck is in possession of a recent shell of this species from the sea near Teneriff.
The shells which Mr Sowerby, in his Mineral Conchology, has figured under the genus Ellipsolithes, have the whorls conspicuous, although the mouth clasps the body whorl. But it is easily distinguished from the other genera with which it is related by its elliptical form.
The genus Discorsis of Lamarck (formerly called by him Planulites) bears a considerable resemblance to the nautilus in form, but the whorls are all apparent, and the partitions entire. The following species of the genus nautilus of Montagu, may be inserted in this genus, viz. crassulus, inflatus, carinatus, Beccarii and Beccarii perversus. Were we acquainted with the position of this last shell in the animal, we might, on account of its sinistral whorls, consider it as belonging to a new genus. The serpula lobata and concamerata of the same author, are nearly related to the present genus. But the circumstance of their being fixed shells, would induce us to form a new genus for their reception, which we term Lobatula.
In the genus Rotalia, the spires approach to a conical shape, and the margined trigonal aperture is reflected towards the base of the shell. It consists of shells which are now found in a fossil state.
The Nautilus spirula of Linnaeus has afforded characters for the construction of a new genus termed Spirula. The whorls are separate, the mouth orbicular, the partitions perforated by a tube, and the last turn of the spire prolonged in a straight line. This last character was unknown to Linnaeus, who had only seen the spiral body of the shell.
The genus Spirolina has the last turn of the spire produced like the preceding, but the whorls are contiguous. The partitions are perforated by a tube. The Nautilus semilittus and subarctatus of Montagu are of this genus.
The genus Lituola is allied to the spirula and spirolina in the production of the last whorl. The spires of the body are contiguous, and the partitions are pierced by a number of holes.
In the preceding genera the inner walls of the cavity are simple; but in the two following, the walls are formed into joints by sinuous sutures. The first of these is the Ammonites, including those shells which have been termed cornua ammonis. The origin of this name is, by some, sought for in their resemblance to the horns of a ram; by others, to their having been found near the temple of Jupiter Ammon, in Upper Egypt. By the Indians, the Ammonites sacer is considered as a metamorphosis of the god Vishnu, and termed by them salgram or salgraman. It is found among the pebbles of the Gandica where it joins the Ganges. In this genus the whorls are contiguous, spiral, depressed, and obvious.
The Orbilites of Lamarck differs from the ammonites in the circumstance of the last whorl embracing and concealing the others. In both the syphon is marginal. The ammonites discus of Sowerby appears to be of this genus.
Nearly allied to the preceding is the Turritites of Monfort. It is similar in internal structure, but while the shells of the former are spirally discoid, those of the present genus are spirally turreted, resembling a Turbo or Turricula. Four species are figured by Sowerby in his Mineral Conchology, Vol. I.
The Genus Scaphites, formed by Parkinson, possesses very peculiar characters. It commences with a depressed volution, the last turn of which, after being enlarged and elongated, is diminished and reflected inwards.
2. Multilocular testacea with the shell produced. It must be confessed, that the genera of this section are but imperfectly understood. The recent kinds are too small to admit of any investigation of the animal, so that we are left entirely to conjecture. The genus *Hippurites* is of a conical form, and either straight or crooked. Within it is transversely chambered, and furnished with two lateral, longitudinal, obtuse, converging, ridges. The last chamber is closed by an operculum.
In the *Orthocera* the shell is straight or slightly bent, and conical. The chambers are distinct, and pierced with a tube. We possess on our shores many minute species of this genus.
The genus *Baculites* of Faujas St Fond, possesses a structure similar to the ammonites, the inner walls being articulated with sinuous sutures, and the partitions perforated. The shell is fusiform or bent into two parallel limbs. Mr Parkinson has contributed greatly to our knowledge of this genus, and has termed it *Hamites*. We prefer the name of the original discoverer to that of our English naturalist, which is very faulty. For, according to Play, "Hammites ovis piscium similis est."
In the *Belemnites* the shell is straight, conical, pointed, solid at the summit, and furnished with a lateral gutter. There is seldom more than one of the cells apparent, of a conical form, the older ones having been effaced in succession. The genus *Tulaxodes* of Guettard is not, perhaps, entitled to be considered as distinct.
The *Amplexus* of Sowerby belongs to this division. It is nearly cylindrical, divided into chambers by numerous transverse septa, which embrace each other with their reflected margins. It contains one species from the limestone rocks of Ireland.
3. Multilocular testacea of a globular form. The first genus of this section is the *Miliola*. The shell is composed of three or four oval cells, turning round an axis parallel to their longest diameter. Many recent species of this genus are common on our shores; they were included by Montagu in his genus *Vermiculum*.
In the *Renolina* the cells are narrow, linear, unilateral, curved into a part of a circle, and all situated on the same plane. The smallest cell forms a little arch round a marginal axis, and the others are placed contiguous to this on the same side. The species are all fossil.
The *Gyrogonia* is a shell of a spheroidal form, composed of linear, curved, grooved, pieces, terminating in two poles. The external surface is obliquely spiral, the spires terminating at each pole. Found only in a fossil state.
The shells of the genus *Nummulites* are remarkable for their lenticular form. The external surface is smooth, and the cells concealed, but internally the transverse cells are disposed in a spiral discoid form. The cells are imperforate; they are the Camerinae of Bruguiere,—the Helecites of Guettard,—and the Discolithes of Fortis. This last author supposes, that they are formed in the interior of an animal analogous to the Sepia. The same opinion may, with propriety, be entertained of many other genera of multilocular testacea. Faujas St Fond found a recent specimen of a nummulite among the fragments of the Corallina officinalis, brought from the island of Corsica.
It is probable that the genus *Lagena*, formed from the serpulae *lagena* of Walker's *Testacea mi-
nutia Rariora*, belongs to the multilocular testacea; as conchology in some of the species we have observed the appearances of internal divisions.
As connected with this division of the Linnaean genera, we may take notice of the British shell called by Lightfoot *Nautilus lacustris*. (Phil. Trans. LXXVI. Tab. 1.) The very circumstance of its being a fresh water shell, distinguishes it sufficiently from all those which we have been considering, and its other characters are likewise peculiar. The partitions are distant, and consist of three testaceous plates, not united, which leave a sufficient opening between them to allow the animal to protrude and withdraw itself. It constitutes a distinct genus, which we have termed *Segmentina*, from the trivial name bestowed on it by Solander, which refers to the structure of the septa. Its place in the system is next to the genus Planorbis.
These genera of multilocular shells which we have enumerated, are those which have been established with the greatest attention. Many other genera might have been enumerated, particularly those formed by Montfort, but the character given of them by Cuvier will satisfy the curiosity of the reader. When speaking of the *Conchyliologie Systematique* of that author, in reference to this subject, he says, "On presque toutes les espèces et même des variétés sont érigées en genres."
19. *Conus*. This genus is so very natural, that it has undergone no changes since the days of Linnaeus, except the addition of new species. That author was acquainted with thirty-five species and a few varieties; but M. Hawss communicated to Bruguière descriptions of one hundred and forty-six, from specimens existing in his own cabinet. We cannot boast of any British species.
20. *Cypraea*. This genus is equally natural as the former. It has undergone no change since the days of Major. The *C. Europaea* and *voluta* are found on our coasts.
21. *Bulla*. This genus presents to the mere Conchologist a source of great perplexity. It displays at once the absurdity of dividing the molluscous animals into testaceous and naked, since no such distinction is observable in nature. Many of the shells which were formerly included in this genus are found to be contained within the common integuments of the animal. It was this circumstance which induced Linnaeus to separate the Limax and the Aplysia from the vermes testacea. Both of these have shells, but they are concealed. In imitation of the same principle, Lamark has formed a new genus among the naked mollusca, called *Bullae*, for the reception of those bullae in which the shell is concealed. The Bulla *aperta* is the type of the genus. The Bulla *plumula* of Montagu is another shell included in the animal, which is very closely connected with the genus *Pleurobranchia* of Cuvier. (Annales du Mus. V. 269.) It may be asked, Are all the other Bullae found in similar situations, and consequently do they belong to the naked mollusca? Lamark considers, and apparently with reason, that all those which are distinctly spirally involuted, and ornamented with colours, are not entirely inclosed in the cloak of the animal, and ought therefore to be ranged with the testaceous mollusca. How few British species does this character include? As originally constituted, the genus of Linnaeus contained species of very different characters, so that many new genera have been formed. To Bruguiere, Lamarck, and Draparnaud, we owe all the improvements which have taken place.
The modern genus Bulla includes those shells which correspond with the following character: "Testa univalvis, convoluta, ovato-gibbosa vel cylindracea; spirae non exserta, apertura longitudine testae; labro acuto." The B. ampulla is the type of the genus.
The genus Ovula, instituted by Bruguiere, is more nearly related to the Cypraea than to the Bulla. It differs however from the former, in the left margin of the lip being smooth; and from the latter, in the edges of the mouth being rolled inwards, and in the shell being produced at both ends. The B. ovum of Linnaeus is the type of the genus; the B. patula of Pennant.
The Bulla terebellum has been employed by Lamarck to constitute his genus Terebellum. The canal at the base of the mouth, and the truncated pillar, furnish the generic characters.
Linnaeus was, for some time, uncertain where to place those shells which he at last inserted in the genus Bulla, under the trivial names Ficus and Rapa. These, with a few of the murices of the same author, constitute the genus Pyrula of Lamarck. Its canalicated base removes it from the Bullae, while the short spire, the swelling of the last whorl, the smooth pillar, and pyriform shape, distinguish it from all those with which it is apt to be confounded. It is more nearly allied to the Fusus than to any other.
In the genus Achatina of Lamarck, the pillar is truncated as in the Terebellum, but the base of the mouth is entire. It is represented by the Bulla achatina of Linnaeus. To this genus we may refer the Buccinum acicula of Muller, which is found in England, and the Helix octona of Linnaeus, erroneously considered as a native of Britain.
The preceding genera consist of species which live in the sea. The B. virginea is a terrestrial shell, and ought to form a distinct genus next the Bulinius. The B. fontinalis, hypnorum, and rivalis, reside in fresh water. They have, with much propriety, been formed into a distinct genus by Draparnaud, which he calls Physa. They are all sinistral shells, and will require further division when the form of the animal shall become the basis of generic distinction. The fontinalis and hypnorum are natives of Britain.
22. Voluta. This genus, as originally formed by Linnaeus, depended, as he informs us, on the plicae of the pillar, "volute genus facillime distinguitur columella plicata." But as this character belongs to many shells otherwise very different in form, succeeding Conchologists have separated many species from the genus, and reduced it within more natural limits. As it now stands, it is thus defined: "Testa univalvis, ovata, subventricosa, apice papillari; basi emarginata. Columella plicata; plicis inferioribus, majoribus, vel longioribus." The type of the genus is the Voluta musica.
Bruguiere removed from the Linnaean genus those species which are destitute of a groove at the base of their mouth, and of which Lamarck formed the genera Auricula, Tornatella, and Volvaria. In the latter the spire is not produced; in the former it is produced. To the genus Auricula, which contains land-shells, the V. auris-midae and auris-jude belong. The V. tornatilis is the type of the genus Tornatella. In his reference to the genus Volvaria, Lamarck quotes the Bulla cylindracea of Pennant and Da Costa, as if they were one and the same. But Pennant's shell is a true Bulla, while that of Da Costa is regarded as the Voluta pallida of Linnaeus, and probably belongs to this genus.
In the genus Oliva, the turns of the spire are separated externally by a very distinct gutter or canal, and the pillar is obliquely striated. The Voluta oliva of Linnaeus contains many different species of this genus, which are remarkable for the smoothness of their surface, and the brilliancy of their colours.
The Ancilla, which, like the former, is of a subcylindric form, is destitute of the groove which separates the whorls, and is characterized by an oblique callous ring at the base of the pillar.
In the genus Mitra of Lamarck, the spire is pointed instead of ending in a small knob, as in voluta, and the plicae of the pillar increase in size from the base upwards, which is the reverse in that genus. The V. episcopalis of Linnaeus is the type of this genus, which contains many species much sought after by collectors.
In the Columbella, the shell is oval, the spire short, and the inner edge of the right lip is swollen. The V. mercatoria is the type of the genus.
The Marginella is very distinctly marked by the prominent callous collar which surrounds the outside of the right edge of the shell. The opening of the mouth at the base is scarcely grooved. The V. glabella is the type of the genus.
The Cancelleria is nearly related to the genus columbella, but the absence of the swelling of the lip, and the presence of the compressed sharp plicae of the pillar, furnish sufficiently obvious characters of distinction. The V. cancellata of Linnaeus is the type of the genus.
In the genus Turbinellus the shell is turbinated, subfusiform, and canalicated at the base, having from three to five transverse compressed plicae on the pillar. The V. pyrum is the type of the genus. Is not the V. hyalina of Montagu nearly allied to this genus?
23. Buccinum. This is another of the Linnaean genera of shells, which has undergone great alterations. As originally constructed, it embraced many distinct groups of shells, which Bruguiere and Lamarck have since formed into genera. The restricted character of the genus Buccinum is thus defined by the last mentioned author: "Testa univalvis, ovata vel elongata. Apertura oblonga, basi emarginata, nudata, canali nullo. Columella convexa plana."
Bruguiere separated the genus Cassis, in which the opening is oblong and denticulated on the right side, with a short canal towards the back of the shell. The right margin has a callous border. The Buccinum cornulum of Linnaeus is the type of the species. The genus *Terebra* was likewise formed by the same author. It is remarkable for its turreted form, the spire being at least twice as long as the mouth, and the pillar at the base twisted. The *B. maculatum* of Lin. is the type.
In the genus *Nassa* the groove in which the mouth terminates is reflected as in Cassis, but the left edge of the mouth is callous, and forms upon the pillar a transverse fold. The *B. arcularia* of Lin. is the type.
The *Purpura* is readily distinguished from the Buccinum and Murex, with which it has often been associated by its naked compressed pillar, ending in a point at the base. It includes our common littoral shell the *Buccinum lapillus*.
The genus *Dolium* is distinguished by its bellied forms and transverse rings, together with the margin on the right side being denticulated its whole length. The *Buccinum galea* of Linnaeus is the type of this genus.
The genus *Harpa* is well known, and is distinguished by its sharp parallel longitudinal ribs. The pillar is smooth and pointed at the base.
In the genus *Eburnea*, the shell is smooth, and the pillar umbilicated and subcanaliculated at the base. The *Buccinum glabrum* is the type of the genus.
24. *Strombus*. This Linnean genus is now converted into a family, distinguished by the right margin changing its form with age, and having towards the base an indenture or sinus. It contains three genera, Strombus, Rostellaria, and Pterocera.
In the genus *Strombus*, the canal is short, the right margin is simple, and ends in a sinus. The *S. pugilis* of Linnaeus is the type of this genus.
In the *Rostellaria* the canal is produced into a long beak, the right edge of the mouth is entire, and rests above on the spire, and is sometimes decurrent. The sinus is contiguous to the canal. The *R. cornuta* of Mart. *Conch.* IV. Tab. 158, f. 1495, is the type of the species.
In the *Pterocera* the canal is also lengthened, but the right margin is dilated and digitated with a sinus near the base. The *Strombus Pes-Pelicanii* of our shores is of this genus.
25. *Murex*. The modern genus of this name is thus defined by Lamarck: "Testa univalvis, ovata, vel oblonga; basi caniculata; suturis varicosis-turridis, sub asperis, longitudinibus, et persistentibus." In consequence of this restriction, the five following genera have been instituted.
In the genus *Fasciolaria*, the spires are destitute of those longitudinal ribs which the Murices always exhibit, while the pillar is furnished with two or three oblique folds. The *Murex tulipa* of Linnaeus is the type of this genus.
The shell of the genus *Fusus* is lengthened, generally fusiform, destitute of longitudinal ribs, and bellied in the middle or lower part with a smooth pillar and lengthened canal. The *F. longicauda*, Lister, Tab. 918, f. 11, A, is the type.
The *Pleurotomia* is distinguished from the preceding by a sinus or groove, which appears on the margin of the right edge of the mouth, near its summit. It is represented by the *M. Babylonius* of Linnaeus.
The genus *Clavatula* differs from the former in possessing a short canal, and ought never to have been separated. We may refer to this the *Murex sinuosus* of Montagu, and *M. emarginatus* of Donovan.
In the genus *Cerithium*, the mouth is oblique, terminating below in a short truncated or recurved canal, and having at the upper part a gutter more or less produced. The *Tympanotonos asper* of Mart. *Conch.* 4. p. 314. Tab. 156, f. 1473, and 1474, is the type of the genus.
26. *Trochus*. This is a very natural genus in the Linnean system, and has undergone few alterations in the hands of modern Conchologists. The *T. perspectivus* has given rise to a new and very obvious genus, termed *Solarium*, characterized by the internal spiral edge of the umbilicus being crenulated. Another species, the *T. labio*, is the type of the genus *Monodonta*, which contains shells of an oval form, with a rounded mouth, furnished with a tooth, formed by the truncated projecting base of the pillar: the two margins are separated. The turretted trochi of Linnaeus constitute the genus *Pyramidella*.
The *T. terrestris* of British writers is so imperfectly described and figured, that it is impossible to assign it a place in the system. It is nearly allied to the helix.
27. *Turbo*. This very extensive genus has been greatly dismembered by modern Conchologists, in consequence of Lamarck having restricted the character in the following terms: "Testa univalvis, conoidea vel subturrita. Apertura integra rotundata, edentula; marginibus superne semper disjunctis; columella basi planulata." Our *T. litoralis* is a good example of the restricted genus. In noticing the new genera which have been formed, we shall begin with the marine shells.
In the genus *Scalaria*, the mouth is circular and bordered, with the margins united. The spires are covered with raised, edged, slightly oblique, longitudinal ribs. The famous wentletrap is the type of the genus.
Lamarck thus defines his genus *Delphinula*: "Testa univalvis subdiscoidea vel abreviato conica, solida, margaritacea, umbilicata; anfractibus subaspersis. Apertura rotundata, marginibus orbiculatim connexis." The *T. delphinus* is the type of the genus. There are many species of turbinates common on our shores, which are excluded by the preceding characters from the genera Turbo and Delphinula, such as the striatus, cingellus, Brycerus and others. They are distinctly turreted, with the margins of the mouth united, and may constitute a genus to be termed *Cingula*.
The Turbo terebra of Linnaeus serves as the type of another genus, termed *Turitella*, in which the margins of the mouth are disjoined, the spire regularly turreted, and the lip emarginated by a sinus. Nearly allied to the preceding is the genus *Phasianella*, which Lamarck thus defines: "Testa univalvis, ovata vel conica, solida. Apertura longitudi- Perhaps a rigorous examination of the turbines of British writers might justify the formation of one or two new genera; yet we shall content ourselves with noticing those species with which we have formed the genus *Odostomia*, in which the columella is furnished with a tooth. The *Turbo interstincta*, unidentata, plicata, Sandivicensis and insculpta of Montagu, are of this genus. They have no resemblance in their structure to the Linnaean volute; although they have been inconsiderately associated with them by the authors of the *Descriptive Catalogue*. The preceding genera are formed of marine shells; those that follow live on the land.
In the genus *Cyclostoma*, the mouth is circular, with united and often reflected margins. The animal is furnished with an operculum. The *T. elegans* of Montagu is the only British species of the genus.
The species which are related to the *T. bidens perversus* and *muscorum* of Linnaeus, constitute a very natural family, which may be termed *Pupacea*, distinguished by the mouth being furnished with teeth or testaceous laminae, and the last whorl nearly the same or less than the preceding. Perhaps the most convenient way of dividing them is into two sections, the first including the dextral, and the second the sinistral shells.
The dextral pupacea form two genera. The *Pupa*, as originally constructed by Lamark, was equally faulty with many of the old Linnaean genera. As we have restricted it to include dextral shells, with the animal possessing four tentacula, with eyes at the tips of the two longest, we can receive into it the *muscorum*, *sexdentatus*, *tridens*, and *juniperi* of Montagu. In the genus *Carychium*, formed by Muller, the tentacula are only two in number, with the eyes placed at the base. It is represented by the *T. carychium* of Montagu.
The sinistral pupacea form likewise two genera. The first, which is the *Clausilia* of Draparnaud, contains sinistral shells, with the animal furnished with four tentacula, with eyes at the tips of the two longest. This contains the following British species,—*perversa*, *nigricans laminata biplicata*, and *labiata*. The other genus, called *Vertigo*, was formed by Muller. The animal possesses only two tentacula, with the eyes on their tips. The *T. vertigo* is the type of the genus.
28. *Helix*. Linnaeus, in constructing this genus, attended only to the character of the mouth being contracted or lunated, without regarding the habits of the animals, or even the other forms which the shells exhibited. Hence he has united globose, discoid, and turreted, terrestrial, fluviatile, and aquatic shells; animals with two and with four tentacula, with and without an operculum, oviparous and viviparous.
The marine species of Linnaeus are few in number. The genus *Janthina* of Lamark, has been formed from the *H. janthina* of Linn. a species which has lately occurred at several places of the Irish coast. The opening is triangular, and there is an angular sinus at the right edge. The shell, which Linnaeus terms *H. haliotoides*, is completely concealed in the animal, and belongs to the genus *Sigaretus*, among the naked mollusca of Lamark. There are many marine shells inserted in the genus *Helix* by British writers, which either belong to the restricted genus *Turbo*, or to the *Vermicularia*.
The further reduction of the Linnaean helices depends on the separation of the terrestrial from the fluviatile shells, and subdividing these according to the characters furnished by the different groups.
Among the terrestrial shells, the restricted genus *Helix* is by far the most extensive. It contains those shells which are subglobose, with a convex spire; the opening entire, wider than long, and diminished in its upper part by the projection of the last turn but one of the spire. The animal is furnished with four tentacula, with eyes at the tips of the two longest. The *H. pomatia* is the type of the genus.
The genus *Bulimus*, as originally constructed by Bruguiere, was faulty in the extreme, but Lamark has new modelled it so as to include those land shells which are turreted or conical, with the mouth larger than broad, and having, in general, the margin reflected with age. Like the Helices, they have no operculum, and possess four subulated tentacula. The following are known as British species, *B. obscurus*, *lubricus*, *Lacklamensis*, and *fasciata*.
From the *Helix succinea* of Muller (the putris of Montagu and Donovan, not of Linnaeus) Draparnaud has formed the genus *Succinea*. The mouth is large in proportion to the size of the shell, and effuse at the base, with the outer lip thin, and the pillar attenuated. We are at a loss to account for the conduct of Lamark in substituting a new name for this genus without any apparent reason, and thus adding to the synonymes with which the science is already oppressed. The name first employed by Draparnaud, indicates one of the most striking characters of the type of the genus, whereas the term Amphibulina, used by Lamark, is founded on a mistake, and is apt to mislead. The *H. succinea*, although found in damp places, is not amphibious. It never enters the water voluntarily. Indeed, Muller says, "Sponte in aquam descendere nunquam vidi, a contra quoties cum aquae immisi, confestim egressiebatur." The same remark is made by Montagu, and we have often witnessed its truth.
The *Helix pellicula* of Muller has been formed into a new genus by Daudebard, which he termed *Helico-limax*, but which Draparnaud, to avoid the use of a hybrid name, changed for the term *Vitrina*. Lamark has placed it among his naked mollusca, as the shell merely covers the superior parts, and the animal is furnished with a shield.
The fluviatile shells, included by Linnaeus in his genus *Helix*, may, for the sake of present convenience, be considered as forming two sections, viz., those with and those without an operculum. To the former belongs the very natural genus *Lymnea*, containing conical or turreted shells, with the right lip joined to the left at the base, and folding back on the pillar. The *H. stagnalis* of Linnaeus, is the type of the genus, of which we possess ten British species. Two of these are truly amphibious, the octanfracta and fossaria. The genus Planorbis, instituted by Geoffroy or rather by Petiver, is remarkable for its discoid form, the spire revolving nearly in a horizontal line, so that all the whorls are obvious on both sides. Cuvier observed that the P. cornex was a sinistral shell, and it remains to be ascertained whether the whorls in the other species have a similar direction. We possess nine British species of this genus.
The operculated divisions of fluviatile helices, is more numerous than the preceding, containing at least six genera.
The genus Valvata was instituted by Muller to include depressed shells with an orbicular mouth, the animal, furnished with three tentacula and a plumose appendage, considered as the branchiae. The V. cristata (Helix crist. of Montagu), and piscinalis (the Turbo fontinalis of Montagu), are natives of this country.
The genus Vivipara, instituted by Geoffroy, and afterwards employed by Montfort, is represented by the H. vivipara of Linnaeus. It is the same as the Paludina of Lamark. The shell is ovate or oblong, with a regularly elevated rounded spine. The aperture is entire, with the two lips united angularly at the summit. The type of the genus and the V. tentaculata, are natives of Britain.
In the genus Ampullaria of Lamark, the shell is globose, the base umbilicated, and the mouth longer than broad. The H. ampullacea is the type of the genus.
In the genus Helicina of Lamark, the mouth is semilunar, the pillar callous and compressed below. The H. neritella, Lister, Conch. Tab. 61, fig. 59, is the representative of the genus.
In the genus Melania of Lamark, the shells are turreted, longer than broad, effuse at the base, with a twisted solid pillar. The H. amarula is the type.
The genus Melanopsis was instituted by Daudin to include the shells termed Melanice by Olivier in his voyage to the Levant. The mouth is lanceolate, the pillar truncated and emarginated above, with a callosity at the base.
29. Nerita. This genus has been subdivided by Adanson and Bruguiere into Nerita and Natica. In the former there is no umbilicus as in the N. erica, and, in the latter, there is an umbilicus, as in the N. camrena. Of the restricted genus nerita, we only possess one species, the littoralis, common on our shores. There are at least six species of Natica of British growth, the largest of which is the glaucina. The fresh water species have been formed by Lamark, with great propriety, into a distinct genus, under the title Neritina. The N. fluviatilis occurs in the English rivers.
30. Halyotis. This genus has been dismembered of those species which are destitute of the perforations on the disk. These have been formed into a new genus, termed Stomatia.
31. Patella. This genus, which at first sight appears so very natural, contains shells which exhibit considerable differences, both in form and structure, when narrowly examined. Geoffroy, with great propriety, separated the fluviatile species under the generic title Ancylus, a genus afterwards employed by Muller. The animal is essentially distinct from the marine patella. There are two species of this genus, the lacustris and fluviatilis, natives of Britain.
The genus Patella, as circumscribed by Lamark, is thus characterized: "Testa univalvis, non spiralis, clypeata vel subconica, imperforata, fissura marginali destituta cavitate simplici." The common Limpet may serve as the type of this genus.
In the genus Fissurella, established by Bruguiere, there is always an opening like a key-hole, near the summit of the shell. The F. graeca and apertura are found on our coasts.
The genus Emarginula is readily distinguished by the slit or indentation which occurs on the posterior margin of the shell. Lamark conjectures that the anus of the animal is situated at the hole at the summit of the fissurella, and at the posterior slit in this genus.
In the genus Capulus of Montfort, the shell is conical, with the summit produced into a beak, more or less recurved, and twisted. The P. hungarica of Lister is the type. Cuvier seems inclined to place in this genus the Bulla velutina of Müller, the Helix lavigata of British authors. The E. fissura is a native of our shores.
The genus Concholepas is furnished with an operculum, and in form and habits approaches the Buccinum. It is represented by the P. integra of Da Costa's El. tab. 2, fig. 7.
In the genus Crepidula, the cavity of the shell is partially interrupted by a simple diaphragm. The P. porcellana is the representative of this genus. The C. chinensis inhabits the British seas.
In the preceding genus, the first approach to the turbinate shell makes its appearance, which becomes more obvious in the genus Calyptraea, in which the cavity is furnished with a spiral diaphragm. The C. eques is the type of the genus, which is related in part to the Trochi. From this genus of Lamark, Montfort has separated the Infundibulum, as possessing a central spiral pillar. Sowerby has figured several species of this last genus in his Mineral Conchology as occurring in a fossil state in Britain.
The Patella unguis now ranks as a bivalve, and constitutes the genus Lingula in the acephalous family Brachiopoda of Lamark. Linnaeus, who never saw more than one valve, placed it among the Patella. Chemnitz, who examined both valves, considered it as a Pinna. These writers had overlooked the figure of the perfect shell, with its tube or stalk, as given by Seba, Vol. III. fig. 16. No. 4. This specimen, which belonged to Seba, passed into the museum of the Stadtholder, and afterwards reached, in company with the spoils of the other Continental collections, the Museum of Paris. Here Lamark examined it, and formed his new genus. And the same specimen enabled Cuvier to investigate its anatomical structure, which he has explained in detail in the first volume of the Annales de Museum. Science has in this instance, as well as several others, profited by the successes of the Ex-Emperor of the French. This genus is destitute of a hinge. The valves are supported on a peduncle, and the shell is opened partly by the relaxation of the adductor muscle of the animal (and not by the external Conchology membrane, as stated by Mr Sowerby), and partly by the issuing forth of its spiral arms, which push asunder the valves like a wedge.
Cuvier has likewise constituted a new genus, which he terms Orbicula, from the Patella anomala of Müller, Zool. Dan. Vol. I. p. 14. t. 5. The under valve is very thin, and fixed; the upper is orbicular, and depressed. It is a member of the same family as the preceding in the system of Lamark.
32. Dentalium. This very natural genus of Linnaeus has undergone no alterations. The Dentalium imperforatum, trachea, and glabrum of Montagu's Testacea Britannica, do not accord with the essential character of the Linnaean genus in being "utraque extremitate pervia." In consequence of this, we formed, some years ago, a new genus for their reception, called Cæcum. They differ from the dentalia in being closed at the apex, and, in a natural arrangement, would probably be placed near the genus Vermicularia.
33. Serpula. This genus has undergone several changes in the hands of modern Conchologists. The S. seminulum has been transferred to the genus Miliola, and the S. filogramum to the Tubipora. Besides these trivial alterations, the character has been greatly circumscribed, so as only to include shells which adhere to other bodies, and are tubular, entire, and flexuous, with a simple mouth, as represented by the S. contortuplicata of Linnaeus. The species which are regularly spiral, discoid, and fixed, as the S. spirorbis, now constitute the genus Spirobis. But as there are both dextral and sinistral shells with this character, we propose to retain the dextral species in the genus Spirobis, and form the genus Heterodiscus for the reception of the reversed species. Under each genus, we can rank six British species.
The genus Vermicularia is formed from those species which, in appearance, resemble the Spirobis, but are not adherent, such as the S. lumbicalis. The shell at the mouth is, in general, somewhat produced. There are two or three minute British shells of this genus. As not very remotely connected with this genus, we may notice the Eumphalus of Sowerby, which he styles "An involute compressed univalve; spire depressed on the upper part; beneath concave or largely umbilicate. Aperture mostly angular." It occurs in a fossil state.
The genus Siliquaria, represented by the S. anguina, is distinguished from the serpula by a longitudinal, lateral, subarticulated fissure, which extends the whole length of the shell.
The genus Penicillus is formed from that curious shell the S. penis, and well known by the name of the watering-pot. The disk is perforated by a number of small holes.
34. Teredo. From this genus, now considered as a bivalve (the tube being regarded as an accessory covering), the Fistulana, of which the T. clava of Gmelin is the representative, has been separated. The external tube in this genus is closed at the posterior extremity, while in Teredo it is open. The S. polythalamia belongs, according to Lamark, to the Fistulana.
35. Sabella. This last genus of the Linnaean vernes testacea has been degraded from its rank in conchology. The covering consists of agglutinated particles of sand and fragments of shells, and bears no resemblance to the testaceous coverings of the true mollusca. It is now placed in company with the Terebella among the annelides.
In the preceding review of the Linnaean genera of shells, the reader will probably have been astonished at those changes which have taken place. In this country we are so much accustomed to the artificial method both in Zoology and Botany, that we often reject, without sufficient consideration, the improvements which the study of the natural method has suggested. In the time of Linnaeus, perhaps, the genera of shells, with a few exceptions, were sufficiently numerous and commodious to embrace all the known species; but since the science has been cultivated with more zeal, in consequence, we must say, of the introduction of the natural method, the number of species has increased fourfold. New genera and orders, and other conventional divisions, have been formed, suited to the state of improvement of the science. The merit of all these improvements did not originate with Bruguiere or Lamark, whose names we have so often had occasion to mention. Many of the modern genera may be traced to the systems which prevailed before the days of Linnaeus,—systems which the Swedish Naturalist, in his desire to simplify, when simplicity was impracticable, too incautiously disregarded.
ON FOSSIL SHELLS.
Besides the shells which are found on the land, and in our lakes, rivers, and seas, and termed recent shells, there are relics of many species found in our marl-pits and limestone rocks, always somewhat altered in their texture, which are denominated fossil shells. While the shells of the former class have been eagerly sought after, few Conchologists have directed their attention to the condition or distribution of the fossil species. Nearly six hundred species of recent shells have been described as natives of Britain, while the fossil species, belonging to our strata, which have been accurately described, fall short of that number. There is, however, reason to believe, that the fossil species are more abundant.
It would have been a pleasant task for us to have entered into the details of this most important subject, but our limits permit us only to trace its outlines. Our remarks, however, we trust, will prove useful to those who are entering this fruitful field of investigation, and will embrace some observations on the systematic characters, condition, situation, and distribution, of these organic remains.
Systematic History of Fossil Shells. The determination of the characters of the fossil species of shells is attended with very great difficulty. The changes which they have undergone, and their union with the substance of the rock, prevent us from ascertaining, with any degree of accuracy, the peculiar marks by which the species are characterized. No trace of the animal remains, to aid us in the investigation, so that all our distinctions must rest on the characters furnished by the shell. This circumstance should prevent us from placing much confidence on the conclusions which have been drawn with respect to The resemblance between fossil species, and those which still exist in a living state.
The difficulty of determining the fossil species, and the reluctance to form new genera, rendered the descriptions of the older writers nearly unintelligible, although their figures are still useful to refer to. Lamarck, aware of the imperfection of the characters of the genera of recent shells, as connected with this subject, and possessing a rich cabinet of the fossil species found in the neighbourhood of Paris, devoted much time to the illustration of this subject, and with great success, as his various papers published in the Annales du Museum, abundantly testify. In this country, Parkinson, in his work entitled Organic Remains of a former World, has added some important illustrations of the genera of Lamarck, and has given some good descriptions of the species found in our rocks. Mr Sowerby, in his Mineral Conchology (publishing in numbers), is giving to the world excellent figures of the British fossil shells; but we regret to add, that he displays too great anxiety to constitute species; and the rocks, in which they are found imbedded, are but imperfectly characterised. But as the figures are well executed, they will prove highly useful to the British Mineralogist, by enabling him to refer to them with confidence, and to give names to those species which he meets with in the course of his investigations.
Chemical History of Fossil Shells. When we consider the elements of which shells are composed, and the nature of their combination, we might be ready to expect that fossil shells would differ but little in structure from recent species. But the case is widely different. In many instances, the confused foliaceous structure which prevailed in the recent shell, has given place to a new arrangement of the particles, and the fossil shell exhibits a foliated crystalline structure. Here solution and precipitation have taken place in the same spot. In some cases the calcareous matter of the shell has become impregnated with foreign ingredients, or has totally disappeared, leaving in its place ferruginous or siliceous depositions. But the most curious circumstance in the chemical history of these fossils, is the preservation of the animal matter of the shell into its original form and order of arrangement, even when the calcareous matter of the shell has been changed into compact or granular limestone. This very important fact we owe to the ingenuity of Mr Parkinson, who, by treating the shell for a length of time with greatly diluted acid, abstracted the calcareous matter, and obtained a distinct view of the cartilaginous membranes of the shell. The student will in general observe, that the cavities of those shells, which present an external opening, are filled with the same sort of matter as the rock in which they are enclosed; while the cavities of the multilocular testacea, which have no external communication, are filled with matter invariably of a crystalline structure, even when not different from the substance of the rock.
Geognostic History of Fossil Shells. It appears evident that the advancement of this branch of Conchology must, in a great measure, depend on the accurate discrimination of the fossil species, and the relations of the rocks in which they are contained. It is only within the last twenty years, therefore, that Conchology, our knowledge of this branch of the subject has been acquired. Werner has contributed largely to our stock of knowledge, but much yet remains to be brought to light. The following notices may be regarded as embracing the principal facts which have been ascertained.
In those ancient strata upon which all the others are incumbent, and which are called Primitive, no remains of shells, or other relics of organized bodies, have hitherto been detected. These rocks are therefore supposed to have received their arrangement previous to the creation of animals or vegetables. In that group of rocks which rests upon the primitive strata, and to which Mineralogists give the name of Transition, fossil shells, as well as the remains of vegetables, have been observed. The shells exhibit such striking peculiarities of form, and bear so remote a resemblance to the recent kinds, that they are considered as the remains of species which do not now exist in a living state on the globe. They are much changed in their texture, and in general intimately united with the contents of the stratum. They are chiefly found in the beds of limestone, sometimes also in the greywacke and clay slate. In the numerous and ill-characterized series of strata which are incumbent on the transition class, and to which Mineralogists attach the term Floetz, the remains of shells are much more numerous. In the older members of this class, such as the red sandstone and independent coal formations, the shells, though generally different in form from those of the preceding class, are still dissimilar to the recent species, and no longer exist in a living state. In the newer members of this class, however, such as the gypsum and chalk rocks, the species bear a much closer resemblance to the existing races, and several species cannot be distinguished from them by any satisfactory characters furnished by the shell. The fossil species found in the rocks of the older members of the class are greatly altered in their texture, and, in many cases, intimately united with the substance of the beds; the shells belonging to the newer members, are much less altered in their form and texture, separate more readily from the surrounding rocks, and appear like recent shells somewhat weathered. The shells are found in nearly all the different kinds of rock, but are more numerous in the calcareous strata. In the alluvial strata, fossil shells are frequently to be met with. The species which here present themselves bear so close a resemblance to the existing kinds, that Conchologists are disposed to consider them as the relics of animals which still exist. In many cases, the prototypes may be found on the neighbouring shore or lake, but in other instances they must be sought for at a greater distance. These shells are found in beds of gravel and sand, and likewise in great abundance in shell marl.
It appears, then, that the shells in the older strata differ specifically from those which the newer strata contain; and that they have belonged to molluscous animals, which no longer exist in a living state on this globe; that, in the newer strata, the fossil shells bear a closer resemblance to existing species; and that in the last formed strata, remains of species actually existing are to be met with. In this distribution of the remains of testaceous animals we likewise perceive that, in the older strata, the inequivalved and multilocular shells are more numerous than the other kinds; and that the canaliculated univalves are seldom to be met with in the transition or older members of the Floetz series, but that they become more numerous in the newer members of the Floetz rocks, and in the alluvial strata. Circumstances of this kind induced Werner to conclude that different formations could be discriminated by the petrifications which they contain. From the difficulty of distinguishing the fossil species, however, joined with our ignorance of their geographical distribution, few Mineralogists have suffered their conclusions to be much influenced by this rule.
It will likewise be observed, that the shells in the newer strata are but little changed, while those in the older rocks are greatly altered in their texture, and in part obliterated. The same power which rendered the rock compact or crystalline, has likewise exerted its influence on the imbedded remains. In the newest strata, this power has scarcely begun to operate; so that the imbedded shells still retain in perfection their original characters.
In examining a limestone quarry, for example, the student will perhaps be surprised to find petrifications of shells in the bed of limestone, while, in the sandstone covering, he witnesses impressions of plants unaccompanied with shells. In order to gain more correct ideas on this subject, let him repair to a marl bog, and he will there find the bed of marl abounding in shells, while in the bed of sand below, on which it rests, or of peat moss, which covers it, he will find exclusively the remains of vegetables. Here let him study the subject, while the strata are yet recent, and while lapidification is only commencing. There is, however, this difference between the shells in the marl and those in the limestone, that individuals of the former species still exist, while no living examples of the latter are known.
Geographical History of Fossil Shells. As the geographical distribution of recent shells is a branch of Conchology to which few have devoted their attention, and about which very little is known, we can scarcely expect to find the geographical distribution of the fossil species more fully illustrated. We know, with regard to the recent shells, that some species which are found in the bays of Norway and Greenland occur also on the shores of the Mediterranean, and that the British Isles have several species in common with Africa and the West Indies. Still we know not, with any degree of accuracy, the geographical range of any one species. Geologists ought, therefore, to exercise a great degree of caution in drawing conclusions concerning the original situation of those shells which they find in a fossil state. When a fossil shell is discovered in the strata of this country, which bears a close resemblance to the recent shells of distant seas; many inquirers, without waiting until they have established the identity of the species, and without any precise information with regard to the geographical distribution of that species, conclude that this fossil shell must have been brought from these distant seas, and conveyed to its present situation by some mighty torrent. Instances of this mode of reasoning could easily be pointed out in the writings of British and Continental Conchology, Mineralogists.
In every country there are particular animals and vegetables, which indicate, by their mode of growth and rapid increase, a peculiar adaptation to the soil and climate of that district. Hence we find a remarkable difference in the animals and plants of different countries. Many shell-fish have indeed a very wide range of latitude, through which they may be observed; but we know, that the same molluscous animals which are natives of Britain, are not found, as a whole, as natives of Spain, while the molluscous animals of Africa differ from both. If the same arrangement of the molluscous animals always prevailed in the different stages of their existence, then we may expect to find the fossil shells of one country differing as much from those of another, as the recent kinds are known to do, so that every country will have its fossil, as well as its recent testacea. Few observations illustrative of this branch of the subject have hitherto been published.
It has often been remarked, that the fossil shells (and the relics of other animals and plants) found in the strata of this country, are very different in their appearance from those shells of the mollusca which at present exist in the country, but that they bear a close resemblance to the existing species of the equatorial regions. This very important observation would lead us to conclude, that the mollusca which lived in this country at the period of the formation of the strata in which they are now enclosed, were influenced by different physical circumstances, from those, by which the forms of the recent kinds are regulated; but it by no means warrants the conclusion, that those shells once lived in the equatorial regions, and that a mighty deluge transported them to their present situation. This last conclusion can never be admitted by those who have witnessed the perfect preservation of the different parts of fossil shells, their valves, spires, protuberances, and delicate spines, still unbroken. Though these species no longer exist, in a living state, in this country (nor on the globe), we must admit the conclusion of Werner (with regard to fossil plants), that they lived and died in the country where their relics are now found.
It would form a very curious subject of inquiry to ascertain the character of those fossil shells which are found in the strata near the equator. If they likewise differ from the recent species of those seas, and if, in appearance, they resemble the productions of arctic regions, we might then speculate, with more success, upon those mighty revolutions which have taken place on the earth's surface, and trace in the mineral kingdom the proofs of those changes which animals and vegetables have experienced. In the meantime, we would recommend the examination of the laws which regulate the physical and geographical distribution of recent shells, as the most suitable preparation for investigating the condition of those extinct races, whose memorials are preserved in strata, differing from one another in structure, position, and composition.
See MOLLUSCA for a classification of shells whose animals are known, and SHELLS for a description of the genera whose animals are unknown.