or KNEE-PAN, in anatomy. See there, no 59.

or LIMPET, a genus of insects belonging to the order of vermes testacea; the animal being of the snail kind. The shells are of that clasps which is called univalves; they have no contour, and are in the form of little pointed cones. They are always attached to some hard body. Their summit is sometimes acute, sometimes obtuse, flatted, turned back, or perforated. The rock or other hard body to which they are always found adhering, serves as a kind of second or under shell to preserve them from injury; and for this reason Aldrovandus and Rondelet have classified them among the bivalves; but in this error they have not been followed by any other writer.

Columna distinguishes four sorts of the lepas or limpets: lepas vulgaris, a sort very common at Naples, of an oval figure and ash-colour. Lepas major exotica, which comes from Spain, the shell is hard, thick, and ribbed in angles, and the rim is denticulated. The lepas agrea, or fylloctris, which is a small shell, irregularly oval, of an ash colour, marked with radii and zones crossing each other, and perforated at the top by an aperture which serves the fish for a vent. And the patella regalis, quia regis mona fit digna; this is of a mother-of-pearl colour within, and is ribbed and perforated in many places; these shells have been found on the back of the sea-tortoise, or turtle, and on a large pinna marina. The distinguishing mark or characteristic of the lepas is to have but one convex shell, which adheres by its rim to a rock, or some other hard substance. There are 36 species of this genus, which are principally distinguished by peculiarities in their shells. Of some of these shells we have given engravings in Plate CCCLXXXII. of which we add the following description:

The limpet marked 1. has large yellow furrows and ridges from the centre to the circumference, which is indented; the eye is perfectly white, and shaped like a nipple.

That marked 2. is perfectly smooth, but radiated with brown streaks, and perforated in the summit.

Fig. 3. is ribbed, and indented at the circumference; its coat is spotted with brown, in a zig-zag form, and its eye is of a ruby colour.

Fig. 4. is a small brown shell, the ribs or striae of which are armed with small white points.

Fig. 5. is striated with radii, reaching from the eye to the circumference, which are crossed by other streaks nearly parallel to the circumference; it is of the usual colour, and its eye is perforated.

Fig. 6. This is white, shaped something like an hand-bell, and has within a protuberance somewhat resembling a clapper.

Fig. 7. is a seven-sided limpet, divided at each angle by ridges from the summit, which form a star on a white ground, variegated with black spots.

Fig. 8. is a small ribbed shell, of a brown colour, and rough; it has a chamber, and a beak-fashioned eye placed at one of its extremities.

Fig. 9. is the finest shell of this species; its size, the fine mother-of-pearl colour on the inside, and the beauty of its red spots without, which have the appearance of tortoise-shell, give it the pre-eminence over all others. It is called the Tortoise shell buckler.

The wild limpet, or patella fera, is a name very improperly applied by Rondilitius and Aldrovand to the aures marinae, or concha veneris, which certainly is not of the patella kind.

the History of Insects, a name given by Lister and other authors to a little husk or shell, found on the bark of the cherry, plum, rose, and other trees, containing an animal within, and useful in colouring. These patellae are of the form of globes, except when they adhere to the tree, and are for the most part of a shining chestnut colour. The husk itself strikes a very fine crimson colour on paper, and within it is found a white maggot which is of no value: this, in time, hatches into a very small but beautiful bee. The size of this bee is about half that of an ant. PAT

Patella. They have a sting like bees, and three spots placed in a triangle on the forehead, which are supposed to be eyes. They are of a black colour, and have a large round whitish or pale yellow spot on the back. The upper pair of wings are shaded and spotted, but the under pair are clear. It might be worth while to try the shells or husks in order to discover whether the colour they yield might not be useful. It is to be remarked, that the deepest coloured husks afford the finest and deepest purple; they must be used while the animal in them is in the maggot form; for when it changes into the bee state the shell is dry and colourless. Lister, who first observed these patellas, went so far in comparing them with the common kermes, as to assert that they were of the same nature with that production: but his account of their being the workmanship of a bee, to preserve her young maggot in, is not agreeable to the true history of the kermes; for that is an insect of a very peculiar kind. He has in other instances been too justly censured for his precipitancy of judging of things, and perhaps has fallen into an error by means of it here. It is very possible that these patellas may be the same sort of animals with the kermes, but then it produces its young within this shell or husk, which is no other than the skin of the body of the mother animal; but as there are many flies whose worms or maggots are lodged in the bodies of other animals, it may be that this little bee may love to lay its egg in the body of the proper insect, and the maggot hatched from that egg may eat up the proper progeny, and, undergoing its own natural changes there, issue out at length in form of the bee. This may have been the case in some few which Dr Lister examined; and he may have been misled by this to suppose it the natural change of the insect.