318 



ORDERS OF REPTILES— CROCODILES AND ALLIGATORS 



General Characters of Crocodilians. — A 



crocodilian is a lizard-like reptile, of very large 

 size, with short, thick legs, a long tail, and the 

 most highly developed vascular system to be 

 found among reptiles. Its back and neck are 

 protected by powerful armor consisting of rough, 

 lozenge-shaped plates of solid bone set in a very 

 thick and tough skin, and arranged in rows, both 

 lengthwise and crosswise. 



Both the tail and the abdomen and throat are 

 covered by a regular arrangement of tough scales. 

 The whole animal is covered by a thin, trans- 

 parent epidermis which is impervious to water. 

 The tail is long, flattened vertically, and fringed 



The eyelids are movable, and the ear opening 

 closes tightly by a flap of skin controlled by 

 voluntary muscles. 



Most saurians are voiceless or nearly so; but 

 the alligator emits a very deep bellow, or roar, 

 which in animals over ten feet in length is much 

 lower on the scale than any fog-horn. 



"The difference between a crocodile and an 

 alligator" (a question that has been asked a 

 countless number of times) consists chiefly in 

 the shape of the head, and the manner in which 

 the teeth are placed in the lower jaw. The typi- 

 cal crocodile has a narrow, triangular head, ter- 

 minating in a rounded point. The head of an 



1. OAVIAL. 



2. ORINOCO 

 CROCODILE. 



5. MISSISSIPPI 

 ALLIGATOR. 



along the top with a row of lofty, saw-toothed 

 scales of great use in swimming. 



The head is a mass of well-nigh solid bone, 

 overlaid by the same thin layer of scaly epi- 

 dermis which covers the body, of the thinness 

 of writing-paper. The nostrils are placed far 

 forward, near the end of the snout. The jaws 

 possess great strength, and are armed with rows 

 of sharp-pointed, conical teeth which are shed 

 when worn out, and renewed. 



The tongue is not free, but is firmly attached 

 to the bottom of the mouth. Its color never is 

 red, but usually is yellowish-white, and some- 

 times pinkish. The iris of the eye is dark 

 green, and the pupil is very narrow, and vertical. 



alligator is broad, with almost parallel sides, and 

 at the end it is broadly rounded off. The canine 

 tooth in the lower jaw of a crocodile fits on the 

 outside of the upper jaw, in a notch close behind 

 the nostrils; whereas in the alligator, the same 

 tooth fits into a pit in the upper jaw. just inside 

 the line of the upper teeth. 



The heads of living crocodilians show wide 

 but progressive variations in breadth, as the an- 

 nexed series of figures reveal. The gavial, of 

 the Canges and Jumna, in northern India, has a 

 snout like the handle of a saucepan, set with 

 four rows of long and very sharp teeth. Alter 

 the gavial of Borneo, its nearest relative is the 

 Orinoco crocodile. At intervals come in the 



