CHORDATA 



325 



leathery skin, with bony dermal scutes on the dorsal side and 

 sometimes on the ventral as well, covered with horny epidermal 

 scales. The eyes are provided with eyelids, and the ears and 

 nostrils are supplied with valves which can be closed when the 

 animal is under water. The jawbones are provided with nu- 

 merous conical teeth, which are firmly set in sockets in the bone. 

 The tongue is thick, attached to the floor of the month, and not 

 protrusible. At the back of the mouth is a structure which 

 prevents the water from entering the lungs if the animal has its 

 mouth open under water. The cloacal opening is a longitudinal 

 slit, and on the ventral wall of the cloaca is an erectile, median 

 copulatory organ or penis. Near the cloacal opening is a pair 

 of apertures which connect the body-cavity directly with the 

 outside ; they are called the peritoneal canals or the abdominal 

 pores and are found in turtles also ; their function is unknown, 

 but they recall the abdominal pores of some fishes, though 

 the structures are probably 

 not homologous in the two 

 groups. The Crocodilia 

 are among the largest 

 existing reptiles and are 

 exclusively tropical, living 



in the mouths and lagoons FlG -326. Gavialis gartgeticus ; head of a gavial. 

 . . (From Luduig-Luunis' Synopsis dei • Thierkunde.) 



01 large rivers all around 



the world ; they seek their prey at night. They include the 



gavials, crocodiles, alligators, and caimans. 



The gavial of India (Fig. 326) is one of the largest of this 



order ; it sometimes reaches 



l * "-3®. 



a length of six meters. It 

 may readily be distinguished 

 from the other Crocodilia by 

 the narrow, elongated snout 

 with its slightly swollen tip. 

 The crocodiles (Fig. 327) 

 belong to the genus Croco- 

 dilus and are found all over 

 the world. They extend over 

 the whole continent of Africa; the crocodile of the Nile was 

 sometimes embalmed by the ancient Egyptians. In India the 



Fie. 327. Crocodilus vulgaris ; head of the croc- 

 odile of the Nile. (From Ludwig-Leunis' Sy- 

 nopsis der Thierkunde.) 



