CRETACEOUS FORMATIONS. 15 



and extensive coalescence of originally distinct bones is a characteristic of the skeleton, 

 the scapula remains distinct from the coracoid, and the persistent suture traverses the 

 glenoid cavity. The coracoid is shorter and straighter in birds than in Pterodactyles, 

 but is commonly broader, and with a longer and stronger anterior process. 



Humerus. 



The portion of bone figured of the natural size in Tab. Ill, fig. 7, shows an 

 articular surface of a reniform figure, convex in its shorter diameter, less convex 

 upon the more prominent half, lengthwise, and slightly concave lengthwise at the side 

 which is hollowed out. The smaller end of the surface (a) has been produced into a 

 process, here broken away, and the fracture is coextensive with the length, in the 

 direction of the shaft of the bone, of the fragment, which is nearly two inches ; the 

 larger end of the articular surface (b) seems not to have sent off such a process ; but 

 the back part of this end is broken away. The pterosaurian nature of the fragment 

 is shown by the thinness of the compact wall of the shaft below the articular surface, 

 and by the wide cancelli. The general resemblance of the articular surface, in shape, 

 to that of the humerus of the Wealden Pterodactyle [Pt. sylvestris, Ow.) figured in 

 the ' Quarterly Journal of the Geological Society,' Dec, 1845, vol. ii, p. 100, fig. 6 ; 

 and to that of the more complete humerus of Pterodactylus suevicus, Qnstd., loc. 

 cit., but especially to the articular surface of the portion of bone of a smaller Ptero- 

 dactyle (Tab. Ill, figs. 14 and 15), which exhibits more distinctive characters of a 

 humerus, have led me to refer the fragment in question (fig. 7) to the proximal end 

 or head of that bone in one of the large species above established by maxillary 

 characters. 



The end of the articular surface (a) answers to the outer' plate or process (g) in 

 Pterodactylus sylvestris, and the fractured surface behind the end (b) might well have 

 been the base of a shorter and thicker process, like that marked f in Pter. sylvestris. 

 Determining, by these analogies, that a is the outer or radial, b the inner or ulnar, 

 end of the transversely extended head of the humerus ; that the convex side is the 

 fore part, and the concave one the back part, of the same bone ; it may next be 

 remarked that the inner half of the fore part of the articular surface is extended further 

 and more convexly upon the shaft than the outer half, which meets the vertical plane 

 of the shaft more abruptly ; but the form of this part of the head of the humerus is 

 better shown in the next specimen. 



This fragment (fig. 8) is the head of the opposite humerus of a Pterodactyle of 

 equal size with the preceding. The boundary of the articular surface near the outer 

 process (a) is very slightly raised, with a few short ridges at right angles, indi- 

 cative of the firm attachment of the capsular ligament ; an oblique line divides the 



