140 CLASSIFICATION OF AMPHIBIANS. 



water serpents ; -while Amphisbcsna is a beautiful repre- 

 sentation^ in many remarkable particulars, of Ccecilia in 

 the class Amphibia, and consequently of all those types 

 which correspond to that division of the Vertebrata. 



(140.) We shall now take a rapid glance at the 

 general contents of these families^ considering the Hy- 

 drophidcE, the Anguidce, and the AmphisbcenidcB, as 

 constituting the aberrant group ; the CrotalidcE, or 

 poisonous snakes, as the typical; and the Coluberid(S, 

 or common snakes, as the sub-typical. 



(141.) The Hydrophid^, or sea serpents, are com- 

 paratively few : they seem to be limited in their geogra- 

 phic range to certain latitudes of the Indian seas, where, 

 however, they are not uncommon. They are chiefly 

 known by the vertical compression of the hinder part of 

 the body and tail : the latter is sometimes so broad, that 

 it may be compared to an oar ; hence these animals swim 

 with the greatest ease : the jaws are differently armed 

 both from those of the Coluberidce and the Ophidcs; the 

 teeth, indeed, in many respects resemble the former, 

 but the anterior maxillaries are longer, and formed pre- 

 cisely the same as the poisonous isolated fangs of the 

 OphidcE. M. Cuvier admits two genera — Pseudoboa and 

 Hydrus: the latter contains the sub-genera Hydrophis, 

 Pelamides, and Chersydrus. It is curious, as showing 

 the tendency of the three aberrant divisions of serpents 

 to unite into one circle, that Linnaeus considered the 

 Pelamides as a true slow-worm, and accordingly named 

 it Anguis platurus. 



(142.) The AMPHisBjaNiD^ are a smaU group of 

 singular-shaped serpents so like the slow-worms in 

 general appearance, that we have more than once ques- 

 tioned, in our own minds, the propriety of separating 

 them so very distinctly by arranging them in different fa- 

 milies. Cuvier, however, has done this; and, under exist- 

 ing circumstances, we shall, for the present, follow his 

 example. In outward appearance they show us a long 

 cylindrical body of equal girth throughout, and with 

 the two rounded extremities so much aUke, that it is 



