PTEROSAURIA. 



271 



an elongation of the antibrachial bones, and more especially 

 to the still greater length of the metacarpal and phalangial 

 bones of the fifth or outermost digit (fig. 97, 5), the last 

 phalanx of which terminates in a point. The other fingers 

 were of more ordinary length and size, and terminated by 

 claws. The number of phalanges is progressive from the first 

 (fig. 97, 1) to the fourth (4), which is a reptilian character. 



Fig. 97. 

 Fossil skeleton of Pterodactylus crassirostris : A, Sketch of living Pterodactyle. 



The humerus, with a larger and more produced pectoral 

 process than in birds, shews characters intermediate between 

 those in that class and in crocodiles. The whole osseous 

 system is modified in accordance with the possession of 

 wings ; the bones are light, hollow, most of them permeated 

 by air-cells, with thin compact outer walls. The scapula and 



