224 EXTINCT ORDERS OF REPTILES. 



The pectoral arch consists of a scapula and distinct coracoid 

 hone, articulating with the sternum as in Birds, hut no clavicles 

 have hitherto hecn discovered. The forc-limh (fig. 572) consists of 

 a humerus, ulna and radius, carpus, and hand of four fingers, 

 of which the inner three are short and unguiculate, whilst the 

 outermost is clawless and is enor^nously elongated. Between 

 this immensely -lengthened finger, the side of the hody, and the 

 comparatively small hind-limh, there must have heen supported 

 an expanded flying - membrane, or " patagium," ivhieh the 

 animal must have heen able to employ as a wing, much as the 

 Bats of the present day. Lastly, most of the hones were "pneu- 

 matic" — that is to say, loere holloiv and filed with air. 



While the above are the general characters of the Ptero- 

 sauria, there are various points in the anatomy of these 



Fig. 572. — Pterodactylus crassirostris. Prom the Lithographic Slates of Solenhofen (Upper 

 (Oolite). In accordance with the view originally entertained, the digits of the hand are here 

 erroneously represented as five instead of four in number. 



singular Eeptiles which may be more closely considered. 

 The head in all the Pterosaurs is elongated and bird-like, 

 the cranial bones becoming early anchylosed, the general 

 fabric of the skull being unusually light, and the orbits being 

 exceptionally large. The occipital condyle is placed on the 

 inferior aspect of the skull, instead of being posterior, thus 

 indicating that the animal was in the habit of standino- in an 



