514 ZOOLOGY. 
vertebre of H. platywrus Cope, of the New Jersey m 1- 
beds, had vertebra nearly as large as those of an elephant, 
while the creature was whale-like in bulk, the neck long and 
flexible, the paddles short. The skull was light, with a 
long, narrow, very flat muzzle It must have been the ter- 
ror of those times; it was about fifteen metres (45 feet) 
in length. (Cope.) 
Order 9. Crocodilia.—The crocodile, caiman, gavial, and 
alligator are the types of this well-known group. They pre- 
sent a decided step in advance of other reptiles, the heart 
approaching that of birds, in having the ventricle completely 
divided by a septum into two chambers ; the venous and arte- 
rial blood mingle outside of the heart, not in it, as in the 
foregoing living orders. The brain is also more like that of 
birds, the cerebellum being broader than in the other rep- 
tiles. The nostrils are 
capable of closing, so 
that crocodiles and 
alligators draw their 
prey under the water 
and hold them there 
until they are drown- 
ed; but they are 
Fig. 451.—Head of the Florida Crocodile.—after Obliged to drag them 
nay ashore in order to eat 
them. Theskin is covered with horny, epidermal scales. The 
conical teeth are lodged in sockets in the jaws. The vertebrae 
are concave in front and convex behind, or the reverse ; the 
quadrate bone is immovable. The feet are partly webbed. 
The crocodiles and gavials appeared during the Jurassic pe- 
riod, but the early forms were marine and like gavials, the 
head being long and narrow in front, with biconcave verte- 
bre. They lay from twenty to thirty cylindrical eggs in the 
sand on river banks. The crocodiles are distributed through- 
out the tropics, even Australia; the gavials are mostly con- 
fined to India and Malaysia, and also Australia, The group 
is represented in the Southern States by the alligator (4. 
Mississippiensis Daudin). It is nearly four metres (10-12 
feet) long; while the Florida crocodile (C. acutus Cuvier, 
