364 ZOOLOGY. 



those without, ophidian: as ophidian may be cited the viper, 

 rattlesnake (Fig. 365), cobra (Fig. 346), as venomous; and 

 as harmless snakes, the common snake or coluber, the boa,* 



Fig. 366. The Crocodile. 



and python. The order saurians comprises crocodiles (Fig. 

 366), lizards, chameleons (Fig. 351), geckos (Fig. 350), the 

 agama (Fig. 364), the iguana, &c. 



CLASS OF BATRACHIANS. 



471. The batrachia or amphibia were long confounded 

 with the reptilia ; when young they breathe by branchiae or 

 gills, and resemble fishes in the general conformation of the 

 body ; but they change their forms and acquire lungs before 

 becoming adult. 



Like fishes and reptiles, they are cold-blooded animals, 

 their circulation is incomplete, and their respiration com- 

 paratively inactive. The skin is naked or unarmed, the 

 skeleton very incomplete, and the heart is composed of a 

 single ventricle and two auricles. 



In their external form they vary considerably, some resem- 

 bling lizards, and even serpents, but generally the body is 

 flat, short, and thick, without a tail, with well-developed 

 limbs. 



472. In their mode of development they resemble 

 fishes ; whilst in the egg, the young animal is not surrounded 

 by the membrane called amnion, and which is always present 

 in the three preceding classes; neither have they an allantois, 

 which plays an important part in the economy of tbe chick 



* Travellers are cautioned not to be misled by the names given to serpents 

 by naturalists. The boa fasciata of Schneider is a most venomous and 

 dangerous snake.- K. K. 



