198 ZOOLOGY. 



Order 5. CrococUUa. — The crocodile, caiman, gavial, and 

 alligator are the examples of this well-known group. They 

 present a decided step in advance of other reptiles, the 

 heart approaching that of birds, in having the ventricle 

 completely divided by a partition into two chambers; the 

 venous and arterial blood mingle outside of the heart, not 

 in it, as in the foregoing orders. The brain is also more 

 like that of birds. The nostrils are capable of closing, so 

 that crocodiles and alligators draw their prey under the 

 water and hold them there until they are drowned; out they 

 are obliged to drag them ashore in order to eat them, The 



Fig. 240.— Head of the Florida Crocodile. 



skin is covered with large bony, epidermal scales. The 

 conical teeth are lodged in sockets in the jaws. The feet 

 are partly webbed. The crocodiles and gavials lay from 

 twenty to thirty cylindrical eggs in the sand on river banks. 

 The crocodiles are distributed throughout the tropics, even 

 Australia; the gavials are mostly confined to India and 

 Malaysia, and also Australia. The group is represented in 

 the Southern States by the alligator (.4. Mississippiensis). 

 It is nearly two metres (10-12 feet) long; while the Florida 

 crocodile (C. acutus, Fig. 240) in which the jaws are much 

 narrower, is over two and a half metres (14 feet) long. It 

 inhabits the rivers of Florida, where it is very rare, and also 

 the West Indies and South America. The cayman of 

 Guiana belongs to a distinct genus, Caiman, and is char- 

 acteristic of the rivers of tropical South America. 



