REPTILIA. 985 
~_ 
be found in the conversion of the anterior extremities into true wings. It is 
indeed true that one genus of living saurians, Draco, possesses the power of 
gliding through the air, but this is effected by means of the extended ribs 
alone, which, covered with skin, and margining the sides of the body, support 
the animal in its aerial movements, precisely as does the outstretched skin of 
the Pteromys, or flying squirrel. The entire structure of the pterodactyle 
fitted it for living in the atmosphere, where it probably possessed as much, 
if not more, freedom of motion than the bat of the present day. ‘The light- 
ness and hollowness of the bones, the bony connexion of the ribs with the 
sternum, the processes of the ribs, the numerous anchylosed sacral vertebree, 
&c., all conclusively indicate this fact. The external or little finger of the 
anterior extremities, was of enormous development, and a membrane extended 
from this, probably to the tail, including the feet. The remaining four inte- 
rior fingers were of moderate size, and all provided with strong claws. In 
the bats, it is the four external fingers which are greatly developed, and over 
which the wing membrane is stretched, leaving the thumb alone, of normal 
size, and provided with a claw. The elongated jaws were provided with 
teeth arranged at intervals, and each implanted in distinct sockets, to the 
number of from 10 to 34 in each jaw. The food of the smaller species con- 
sisted of insects, the larger preying upon fishes or the marsupial mammalia of 
their day. None of these highly curious animals have been detected in North 
America. 
Fam. 11. Dinosauria. While the Pterosauria inhabited the air and the 
Enaliosauria exclusively the water, the Dimosauria seem to have had the 
dry land as the stage on which they played their part in the economy of 
an ancient world. The species of this family exhibit a striking mammalian 
feature in the anchylosis of five vertebree to form the sacrum. In no other 
saurlans, excepting the pterodactyles, is the number greater than two. 
The bones of the extremities were much developed, with crests for the 
attachment of muscles, and with a medullary cavity in the interior, as in 
mammalia and birds. The species were all of gigantic size, and divisible 
into two sections, the one carnivorous, the other herbivorous. The former, 
including the genera Megalosaurus and Hyleosaurus, exhibited peculiar 
serrated sabre-shaped teeth, arranged in distinct sockets; while the latter, 
embracing Iguanodon (and perhaps Plateosaurus) had teeth not unlike those 
of Iguana, which were pleurodont in their attachment to the jaws. Fora 
long time the single species of Iguanodon was supposed to have attained a 
length of from 70 to 100 feet; and although this size is now denied, yet this 
gigantic saurian must be ranked among the largest of all terrestrial animals. 
Of the four known species of Dinosauria, none have been found out of 
Europe. 
Fam. 12. Labyrinthodonta. This remarkable family should, perhaps, 
in a strictly natural arrangement, come next to or be included among the 
Batrachia, although several features would seem to require a position 
superior to that of the family just mentioned. The more essential differences 
consist in the implantation of the teeth in distinct sockets, and in the 
development of certain of the anterior teeth of both jaws into large and 
489 
