﻿14 FOSSIL REPTILIA OP THE LIASSIC FORMATIONS. 



feeble an indication of divisions into condyles, an absence of a general convexity, and a 

 presence of a well-defined concavity in one condyle, and as well defined a flattened or 

 feebly concave facet in the other condyle, of the distal end of a humerus" (ib., p. 16). 

 The demonstration of the true characters of this end of the humerus, given in Plate I, 

 figs. 13, 14, and d, c, have justified the refusal to regard the articular end of the bone of 

 the large Cretaceous Pterosaur as part of the humerus. Should it prove to be the head 

 of a tibia, what a monstrous flying dragon it would indicate ! 



There is no part of the skeleton of the Bird that more resembles the answerable bone 

 in a Pterosaur than the humerus. But the following, with other differences pointed out 

 in the previous Monographs, are well marked and, as far as my observation goes, 

 constant. 



The pectoral process from the radial side of the proximal expansion of the humerus is 

 relatively longer from base to apex, with a broader, more truncate, or less pointed termi- 

 nation in the flying Reptile : it usually forms a low angle in the Bird. 



At the distal end of the humerus of the Bird the oblong radial condyle is usually 

 more pointed anteriorly j the ulnar one is more extended transversely, and the inter- 

 condylar cleft is widened to a groove. The outer and inner ridges are not connected by 

 a post-condylar transverse ridge. The olecranial surface is more depressed, and the 

 tricipital tendinal grooves are better marked ; but the transverse expansion of the distal 

 end is less in proportion to the breadth of the shaft of the humerus in the Bird than in 

 the Pterosaur. 



Other differences in the Pterosaurian humerus, notwithstanding its adaptive develop- 

 ment to flight, showing departure from the avian, and approach to the crocodilian, type 

 are pointed out in detail in my Monograph (Palaeontological volume for year 1858, issued 

 in 1861, Supplement, No. Ill, ' Cretaceous Pterosauria/ p. 13, Plate III). 



