64 REPTILES OF THE WORLD 



the webbed hind feet are employed in slow, treading 

 fashion to maintain the animal in the desired position. 

 General structure: As this is not a text book, the 

 writer does not propose to dive into a technical review 

 of the anatomy. Certain parts of the structure, how- 

 ever, should be understood by the beginner. Let us 

 first examine the massive, bony head, as about it are 

 several interesting features. The eyes and nostrils are 

 so elevated that the flat portion of the head may lay 

 flush with the surface of the water — or slightly beneath 

 it — while these organs are clear above it and performing 

 their respective functions. Immediately behind each 

 eye is a hinged, bony flap constituting an ear covering; 

 this can be opened and closed rapidly; it is tightly shut 

 as the creature goes beneath the surface. The tongue 

 is very broad, thick and attached by its entire under- 

 surface to the lower jaw; it can be raised and lowered, 

 forming a powerful valve to prevent water from rush- 

 ing down the throat when the mouth is opened. An 

 examination of the dentition shows a generous array 

 of sharp, strong teeth of various sizes, but readily 

 divided — on both jaws — into two series, consisting re- 

 spectively of greatly enlarged teeth and smaller ones 

 behind them. All of the teeth are frequently shed. At 

 their base or root they contain a conical hollow and 

 into this fits the tip of the new tooth, steadily pushing 

 out the old member. It is a long-established custom 

 for the keepers in the New York Zoological Park's rep- 

 tile house to look for teeth when cleaning out the big 

 'gator pool. The pool is cleaned once a week, when 

 the men sometimes find as many as a dozen teeth from 

 the five large alligators on exhibition. Provided with 

 such a formidable dentition, besides jaw muscles of 

 enormous power, the dangerous nature of these huge, 



