348 ZOOLOGY 



SECT. 



tarsals, which were immovably fixed, had a nearly vertical position as in Birds ; 

 the fore-limbs are relatively small, and fossil footprints that have been found 

 indicate that the animal supported itself habitually in a half -erect posture like a 

 Kangaroo, with the fore-limbs raised from the ground. The teeth (Fig. 958) 

 are of a remarkable shape, flattened and with serrated edges, sometimes with 

 vertical ridges which may be serrated. The Dinosauria range from the Trias 

 to the Upper Cretaceous, and were most abundant in the Jurassic and Wealden. 



PTEROSAURIA. 



The Pterosauria or Pteroclactyles are perhaps even more remarkable modifica- 

 tions of the reptilian type than any of the orders that have been hitherto alluded to. 

 The chief peculiarities in the structure of these Reptiles were associated with a 

 flying mode of locomotion, the organs of flight being, as in the Bird and the Bat, 

 the fore-limbs. In the Pterodactyles (Fig. 959) the last digit on the ulnar side 



FIG. 959.-Pterodactylus spectabilis. Three-fourths of the natural size. (From Zittel, 



after H. v. Mayer.) 



of the manus is enormously prolonged and thickened, and supported a web of skin 

 (Fig. 961) which extended backwards to the hind-limbs and the tail. Most of the 

 bones are hollow, and have pneumatic foramina as in Birds (p. 366). The vertebra? 

 are proccelous, except the caudals, which are amphiccelous. The cervical vertebra? 

 are elongated and stout, the neck being of considerable length ; there are three 

 to six anchylosed sacrals. The sternum is broad, with a longitudinal keel. The 

 skull (Fig. 960), set on the neck at right angles as in a Bird, is of large size and 

 resembles that of a Bird in general shape, and particularly in the presence of an 

 elongated pointed rostrum ; the orbits are large, and contain a ring of sclerotic 

 ossifications. The sutures are obliterated as in the skull of a Bird. The quadrate 

 is immovably fixed to the skull. In the pectoral arch the scapula and coracoid 



