PTERODACTYLS. 



467 



which could probably tear through the tough hide of even the Hadrosaurus. While 

 hunting, the Lselaps probably wandered around the lowlands, or swam along the shore, 

 until it arrived within twenty-five or thirty feet of its victim, when, with a spring, it 

 cleared the distance, crushing its prey by the weight of its fall, and tearing it to pieces 

 by means of its stout claws and sharp teeth. The crocodiles must have regarded this 

 "animal as their greatest enemy, excepting the sharks, while the smaller Dinosaurs 

 probably held it in the same esteem as do to-day the jackals the lion, an animal which 

 leaves much that to them is useful. 



Order XI. — ORNITHOSAURIA. 



We have now reached the highest order of reptiles, the members of which, all now 

 extinct, resembled the birds most, of living animals. The fore and hind limbs were 

 specialized for an aerial life; 

 the beak, though often toothed, 

 was, in many forms, encased in 

 horn ; the neck was long and 

 the skull, firm and rounded, 

 with large orbits, strongly re- 

 sembled that of the birds. 

 Though the pelvis and hind 

 limbs were like those of liz- 

 ards, the shoulder-girdle with 

 its keeled sternum and wing- 

 supporting bones were remark- 

 ably avian. In the vital organ- 

 ization, also, a remarkable ap- 

 proach to the birds was made. 

 The optic lobes were pressed 

 below the cerebrum, and the cir- 

 culatory system is believed to 

 have been of warm blood, a sup- 

 position strengthened by the 

 fact that the bones were pro- 

 vided with air-sacs, to which 

 pneumatic ducts lead from 

 the bronchial tubes, a respira- 

 tory system characteristic of 

 only tlie warm-blooded birds. 

 Feathers, however, nor any 

 other means of protection, have 

 not been found with the fossils. The wing consisted of a thin flap of skin, resembling 

 that of the bats, and supported by an elongated ulnar finger. The several members of 

 the order were of varying dimensions, ranging from the size of a sparrow to that of the 

 condor. They were contemporaneous with the Dinosaurs, and formed a peculiar fea- 

 ture of the mesozoic landscape, as they flapped their wings on their journeys through 

 the air, or as they perched themselves, comorant-like, along the shore, in company with 

 the loon-like Hesperornis. 



Fig. 270. — Pterodactyl. 



