232 THE TOWER MENAGERIE. 
upper of which are surmounted by a strong keel, those 
of the tail forming superiorly a dentated crest, double 
at its origin. 
The Alligators constitute a natural subdivision of the 
genus, in which the snout is broad, blunt, and less pro- 
duced than in the true Crocodiles; the fourth tooth on 
each side of the lower jaw enters a hole in the upper 
when the mouth is closed; and the toes are only half- 
webbed. They appear to be exclusively natives of 
America. The present species is distinguished by its 
broad and flat snout, with nearly parallel sides, united in 
front by a curved line; by the peculiar arrangement of 
its nuchal scales; and by the elevated internal margins 
_of its orbits. Its colour is dark brown above, and some- 
what lighter beneath. It is one of the most dreadful 
scourges of the countries which it inhabits, preying 
upon all kinds of animals that come within its reach, 
and sometimes even upon man himself. Our specimen 
was apparently very young, not measuring more than 
three feet in length; but during two years that it was 
kept in the Menagerie it was not observed to have at all 
increased in size. It was fed once a week upon raw 
beef. 
