228 



EXTINCT ORDERS OF REPTILES. 



terms Ornitliosauria, and which he looks upon as most 

 nearly related to, but coequal with, the class Aves. The 

 chief grounds for this conclusion, apart from subordinate 

 skeletal peculiarities, are that the Pterosaurs possessed a 

 brain of an ornithic type of structure, and that some of 

 their bones were pneumatic. 



The Ptcrosauria are exclusively Mesozoic, being found from 

 the Lower Lias to the Middle Chalk inclusive, the Litho- 

 graphic Slate of Solenhofen (Upper Oolite) being particularly 

 rich in their remains. Most of them appear to have attained 

 no very great size, but the remains of forms from the Cre- 

 taceous rocks have been considered to indicate animals with 

 more than twenty feet expanse of wing, counting from tip 

 to tip. 



The chief generic types of the Ptcrosauria are charac- 

 terised as follows : — 



1. Ptcrodadylus (fig. 572), comprising forms with four 

 phalanges in the wing-finger, the jaws provided with teeth 

 to their extremities, and all the teeth being long and slender. 

 The tail is short and movable. 



Fig. 5T5.— Restoration of Dimorphod^jii macronyx. (After Owen.) 



2. Dimorphodon (figs. 574 and 575), comprising forms 

 in which the wing-finger has four phalanges, and the jaws 



