Chapter III 



CROCODILIA— CROCODILES, ALLIGATORS, ETC. 



Crocodiles, Alligators, and their allies, although perhaps 

 not attaining quite so great a length as some of the large 

 constricting snakes, are at any rate by far the bulkiest of 

 living Reptiles. They are elongate, four-limbed creatures, 

 with the body covered with thick scales, some or all of 

 which are underlain by bony plates, those of the back 

 being keeled and elevated in longitudinal ridges, while 

 those of the ventral surface are squarish and smooth. 

 The snout varies much in shape ; in the Alligators it is 

 broad and roundish, in the true Crocodiles, as a rule, more 

 or less pointed, while in the genera Gavialis and Tomistoma 

 it is extremely narrowed, with spatulate end. The eyes, 

 nostrils, and external ears are situated on the upper surface 

 of the head, so that the breathing, seeing, and hearing is 

 unimpaired when the animal is in the water, the upper 

 part of the head being usually raised above the surface 

 when swimming. The nostrils and ears are furnished 

 with movable valves, which are kept shut when the animal 

 is under water, while the eyes are provided with a nicti- 

 tating membrane, as well as with a lower and an upper 

 eyelid. The teeth, which are renewed periodically, are 

 placed in a single row and, unlike those of all other recent 

 Reptiles, are implanted in sockets, those of the upper jaw 

 usually overlapping those of the lower. The digits are 



five to the anterior, four to the posterior extremities, 



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