CROCODILIA. 



Order CROCODILIA. Crocodiles, Alligators, Gavials. 



GENERAL CHARACTERS. The Crocodilians are carnivorous 

 fresh-ivater reptiles of large size, now represented by a few 

 genera, e.g. Crocodilus, Alligator, and Gavialis. 



The skin bears epidermic scales, underneath some of 

 which there are dermic bones or 

 scutes. 



The tail is laterally compressed, 

 and assists in swimming. 



Teeth occur in distinct sockets 

 in the premaxillce, maxilla, and 

 dentaries. 



In modern Crocodilians, almost 

 all the vertebra are procailous. 



The skull has many character- 

 istic features, such as the union 

 of maxillce, palatines, and ptery- 

 goids in the middle line on the 

 roof of the mouth, and the conse- 

 quent shunting of the posterior 

 nares to the very back of the 

 mouth. 



Some of the ribs have double 

 articulating heads, and bear small 

 uncinate processes ; transverse 

 ossifications form so-called abdo- 

 minal ribs. 



The heart is four-chambered ; 

 a muscular diaphragm partially 

 separates the thoracic from the 

 abdominal cavity. 



The cloaca has a longitudinal opening. 

 a grooved penis. 



The Crocodilians are oviparous. The eggs have firm cal- 

 careous shells, and are laid in holes in the ground. 



Skeletal system. Numerous transverse rows of sculptured bony 

 plates or scutes, ossified in the dermis, form a dorsal shield. On the 

 ventral surface the scutes are absent, except in some alligators, in 

 which they are partially ossified. But besides and above the scutes. 



FIG. 301. Lower surface of 

 skull of a young crocodile. 



/.;;/,r., Premaxilla ; ui.v., maxilla; 

 pal., palatine ; o. t. , os tran^- 

 versum ;//., pterygoid ; /., jugal ; 

 Q_/., quadrato-jugal ; (J., quad- 

 rate ; p. 11., posterior nares ; c., 

 condyle. 



The males have 



