120 



HIGH SCHOOL ZOOLOGY. 



erect, thftir forelegs being used for prehensile purposes. We 

 now come to certain forms which lived an aerial life, being pro- 

 vided with organs of flight of a chai-acter peculiar to themselves- 

 In this order, the Pterosauria, (Fig. 89) the limbs were approxi- 

 mately of the same size, but the little finger of the anterior 

 extremity was enormously long and strong compai'ed with the 

 others. It had four joints, and between it, the arms and the side 

 of the body, a web of skin was stretched out, somewhat similar 

 to the web between a bat's fingers. Some of them (Fig. 90) 



Fig. 90— Restoration of Rhamphorhynchtis phylbims. (Marsh), i. 



had a long tail terminating in a rudder-like membrane supported 

 by the spines of the terminal vertebrje. But none of them had 

 anything similar to the plumage of the birds, and we diall 

 afterwards .see that the .skeleton of the bird's wing is constructed 

 on quite a different plan from that of the Pterosaurian. Al- 

 though many members of this gi-oup were small, others attained 

 a "isantic size, one found in Kansas having a stretch of some 

 twenty feet. 



