The Biology of the Crocodilia 7 



The distribution of individual forms will be 

 mentioned again when they are discussed in detail. 



Alligator Mississippiensis 



Since this animal, generally known as the 

 American or the Florida alligator (formerly A. 

 lucius), is the one upon which most of the facts 

 of this book are based, it will be discussed first. 



At this point it may be well to answer the ques- 

 tion that is sure to be asked by someone early in 

 any conversation upon the Crocodilia. The writer, 

 and doubtless every other zoologist, has been asked 

 countless times, "What is the difference between 

 an alligator and a crocodile?" As a matter of 

 fact there is, perhaps, no absolute distinction be- 

 tween the two groups, but there are certain fea- 

 tures that make it easy to distinguish, say, between 

 the American alligator and the American crocodile. 



The most striking difference is in the outline 

 of the head; the alligator has a broad, rounded 

 snout, while that of the crocodile is narrower and 

 more pointed (Fig. 2). Again, in the crocodile the 

 fourth tooth from the front projects slightly out- 

 wards and fits into a notch in the side of the upper 

 jaw, while in the alligator (also in the caiman) the 

 corresponding tooth on each side fits into a socket 

 in the upper jaw and hence is hidden, except in 

 some old animals with very long teeth, in which 

 it may pierce the upper jaw and show from above. 



