REPTILIA. 285 



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 Avith 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 vertebrae, 

 &.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 

 wdiich 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. 



Pam. 11. DinosoHvia. While the Pterosauria inhal)itcd the air and the 

 Enaliosauria exclusively the water, the Dinosauria 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 vertebra to form the sacrum. In no other 

 saurians, excepting the pterodactyles, is the number greater than tAvo. 

 The bones of the extremities were much developed, Avith crests for the 

 attachment of muscles, and Avith 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 Hyloeosaurus, exhibited peculiar 

 serrated sabre-shaped teeth, arranged in distinct sockets ; Avhile the latter, 

 embracing Iguanodon (and perhaps Plateosaurus) had teeth not unlike those 

 of Iguana, Avhich Avere pleurodont in their attachment to the jaws. For a 

 long time the single species of Iguanodon Avas supposed to have attained a 

 length of from 70 to 100 feet ; and although this size is noAv denied, yet this 

 gigantic saurian must be ranked among the largest of all terrestrial animals. 

 Of the four knoAvn species of Dinosauria, none have been found out of 

 Europe. 



Fam. 12. hahyrhithodonta. This remarkable family should, perhaps, 

 in a strictly natural arrangement, come next to or be included among the 

 Batrachia, although several features Avould 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 jaAVS into large and 



489 



