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every animal of the genus which has yet been examined, 

 and may sometimes be traced in their fossil remains. The 

 feet, with five toes before and four behind ; only three of 

 these on each foot armed with nails ; hence, two before and 

 one behind are without nails. The nostrils form a long nar- 

 row canal, terminating in the gullet. The vertebrae of the 

 neck bear a species of false ribs, which, touching at their ex- 

 tremities, hinder the animal from turning its head entirely on 

 one side. The sternum, extended beyond the ribs, gives 

 rise also to a particular species of false ribs, which do not 

 articulate with the vertebrae, but terminate in the aponeurotic 

 expansion. 



The genus is divided into the following subgenera : — 



1. Alligators. — The head oblong, its length being to its 

 width, at the articulation of the jaws, as 3 to 2 ; the length 

 of the skull being more than a fourth of that of the whole 

 head ; the muzzle wide ; the teeth unequal in size ; and, at 

 the least, nineteen, and sometimes twenty-two in number, on 

 each side, below ; and, at least, nineteen, and often twenty, 

 above. The first of the lower pierce, at a certain age, the 

 upper jaw, and the fourth, which are the longest, are received 

 into holes in the upper jaw, in which they are hidden when 

 the jaw is shut. The toes are connected in only half their 

 length by a short membrane. The holes in the skull, behind 

 the eyes, in the species in which they exist, are very small. 



2. Crocodiles (generally so called.) — The head oblong, 

 its length double its width ; the skull being less than a 

 quarter of the length of the whole head. The teeth unequal, 

 fifteen on each side below, and nineteen above ; the fourth 

 tooth of the lower jaw, being the longest on each side, 

 passes through a groove on each side of the upper jaw. 

 The skull has two large oval holes behind the eyes. The 

 hind feet are palmated. 



3. Gavials. — The skull hardly a fifth of the length of the 

 whole head ; the jaws narrow, elongated, nearly cylindrical, 



