Ornithosaurian Genus Oinitliocheiius. 549 



Distal end. 



1. Dorsal and ventral surface slightly convex. 



2. Articular surface a convex roll, compressed more or less 



dorso-ventrally, in the median area. 



3. Preaxial border flat. 



In regard to the proximal extremities affixed to tablet 

 J. a. 13 *, specimens 5 and 6 belong to the same species as 

 far as can be ascertained. No. 6 is not ^vell preserved. An 

 unnumbered specimen is near to 5 and 6, with the articular 

 features less prominent. The main difference between these 

 bones and those of Ornithodesmus latidens lies in the latter 

 being flatter and rapidly lessening in size down the shaft. 

 The former are stouter and reveal little or no decrease 

 distally. Between the two surfaces of the articular end of 

 Ornithodesmus Idtidens there is a transverse ridge across the 

 short diameter of the bone, which fits into the valley between 

 the two condyles of the trochlea of the humerus. This is 

 not seen in the Cambridge specimens ; therefore they 

 probably do not belong to distal ends of the humeri 

 J. a. Q, 21 and 32^ Group K, where a feeble incipient trochlea 

 is to be observed, but to Group B. 



Of the four specimens of the distal ends of the radius, 

 J. a. 12, 1-4, not one belongs to the same genus as Ornitho- 

 desmus latidens, for, although there is a general similarity 

 in form, they difter in details. The dorsal and ventral 

 surfaces of Ornithodesmus latidens are flatter and more com- 

 pressed than any of the Cambridge specimens. The ventral 

 surfaces of nos. 1 and 3 are more concave. In all four 

 specimens, including O. latidens, the articular surface is a 

 complete convexity from the pre- to the postaxial border, 

 and all exhibit more or less constriction of this convexity 

 on both dorsal and ventral borders in the median region. 

 Kos. 1 and 3 belong to the same species. The preaxial 

 border is not flattened in O. latidetis as in the Cambridge 

 specimens, but is robust and convex. The bone is much 

 more concave near the articulation on the ventral surface, 

 preaxial side. There is a longitudinal groove for muscle- 

 attachment, contiguous with the postaxial border on the 

 ventral surface, which is not seen in the Cambridge 

 specimens. In O. latidens on the postaxial side of the 

 dorsal surface there is a well-developed ridge and striae, 

 caused by the fibres of the muscles traversing the bone 



* There is au uumimbered specimeu ou this tablet. 



