The Biology of the Crocodilia ‘i 
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 zodlogist, 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. 
