o National Museum. 3' * 



Crocodiles, lizards, frogs, eels, serpents, and sea tor- 

 toises are of this class. Their command over the 

 lungs; the structure of the heart, and other peculiar 

 organizations, manifest an original destination to either 

 element. _ 



CLASS IV. . PISCES. 

 Heart with one ventricle and one auricle : blood cold and red. 

 They breathe by gills. " The ordinary shape of a fish's 

 eve being much more convex than that of land animals, 

 a'correspondlng difference attends its muscular conforma- 

 tion, viz. that it is throughout calcuUi-'ed for flattening the 



eye. The fins are placed in such relation to each other as 



exactly to balance the body of the fish in the attitude best 

 suited to all conveniences of life. The tails of fish are 

 adapted to progressive motion in water; those of warm- 

 blooded water animals, as Order 7, Cete, Mammalia, are 

 horizontal, or principally adapted to perpendicular motion, 

 having relation to their necessity of rising every two or 

 three minutes to the surface to take breath. Among the 

 peculiar organizations of fish, the most remarkable is ihe 

 air bladder ; the distention or contraction of which faci- 

 litates their ascent and descent in water." — Paley. The 

 peculiar muscular organization of fishes has been lately 

 developed in an interesting manner by Mr. Carlisle, at 

 the Royal Society. 



OuDER T. Nantes. Gills and lungs. Rays of fins cartila- 

 ginous. 

 II. Apodes. No ventral fins. 



III. Jiigidares. Ventral placed before the pectoral fins. 



IV. Tlwracici. Ventral fins under the thorax. 



V. Abdomhmks. Ventral fins in the abdomen be- 

 hind the thorax. 

 Sixty-one Genera. 



CLASS V. INSECTvi:. 

 One ventricle, without an auricle; with antennas. 

 In addition to the piculiar organization ul' insects, the 

 i; t uncjucs- 



