ORDER IV. The ABDOMINALES, have the belly-fins placed behind the pectoral fins.—This order contains 17 genera, viz. Fistularia, Esox, Clupea, Cyprinus, &c. See these articles.
The generic characters of this class are taken from peculiarities in the head, the mouth, the teeth, the nostrils, the rays in the membrane of the gills, the eyes, the general figure of the body, the figure of the tail, the situation of the spiracula, &c.
The specific characters are taken from peculiarities in all the parts above enumerated, and many others.
See further the articles FISH in ENCYCL. and ICHTHYOLOGY in the APPENDIX.
The Fifth Class, INSECTA, is subdivided into 7 ORDERS, the characters of which are taken from the wings. See the article INSECT.