OinitJiosdurian Genus Oniitlioclieirus. 545 



Group B. 



J. a. 6, 4. Proximal end of right humerus. The deltoid 

 crest has its origin far below the condyle, and is apparently 

 slightly oblique to its long axis. The pneumatic foramen is 

 further down the shaft than in J. a. 6, 26 (Group A), and 

 there is a ridge on the preaxial moiety of the condyle. The 

 condyle is not so crescentic, and therefore the horns splay 

 more outwards and the ulnar crest is moderately developed. 



Group C. 



The perfect humerus J. a. 6, 30, whose characters have 

 been given by Seeley, is the type. J. a. 6, 22, 23, 24, 27, 28 

 are proximal ends exhibiting pneumatic forarainse on the 

 ventral surface, and 38, 39, 40, 41 should also apparently 

 have been included, although they are too much abraded to 

 reveal the pneumatic foramen. 



Distal ends. 



Group A. 



J. fl. 6, 21 & 32. Examples belonging to left humeri. 

 They are similar to Oniithodesmus latidens, though one-fifth 

 smaller in the transverse diameter of the distal articulation, 

 and the characters are very weakly developed. The central 

 circular cavity and the transverse valley in no. 32 are filled 

 with phosphate of lime, and thus are not well seen, while in 

 No. 31 these are obscured by the bone being much worn in this 

 region and destroyed on the dorsal margin of the median 

 pit. The ulnar articulation on each bone is also worn, and 

 does not appear to have been as highly developed as in 

 Oniithodesmus latidens. Seeley says* that the '' tnesial 

 condyle in this group appears in every case to be an epiphysis 

 which is wanting." The narrow ridge on the proximal end 

 of the ulna requires a valley to articulate in, and this would 

 be impossible if a mesial condyle had been present. 



J. a. 6, 31. This exami)le possesses tiie same characters 

 as nos. 21 and 32, although in a very incipient stage. It is 

 interesting because the central circular entrance into the 

 bone is not present. In that region occurs a basin-shaped 

 hollow only. 



* 11. G. Seelev, ' Ornithosauriii,' 1.^70, p. 40. 

 Ann. & Mag. N. Ilist. Ser. 8. Vol. xiii. 37 



