NO. 2120. THE FORE L1M5 6P ALLOSAVRUS FRA0ILI8—GILM0RE. 507 



Measurements of humerus . mm. 



Greatest length 310 



Greatest width of proximal end 118 



Greatest width of distal end 100 



Least diameter of shaft 38 



Ulna. — The ulna is expanded and heavy proximally with a less 

 expanded distal end. It exceeds the radius in length but is shorter 

 than the humerus. The proportion being as 1 ::1.17. 



There is a heavy olecranon process (o, fig. 4) that extends con- 

 siderably above the articular surface for the humerus. The surface 

 of this process is roughened for muscular insertion. The olecranon 



process is less well 

 developed in Cerato- 

 saurus nasicomis and 

 appears to be entirely 

 wanting on the ulna of 

 Ornitholestes Tiermani. 

 The articular sur- 

 face for the humerus 

 is comparatively nar- 

 row transversely, 

 with a shallow con- 

 cave surface antero- 

 posteriorly. The con- 

 cavity on the proxi- 

 mal end for the recep- 

 tion of the head of the 

 radius is shallow. 

 The shaft of the ulna 

 is slender, suboval in 

 cross-section, and in a 

 distal direction, grad- 

 ually expanding into a moderately large end, the greatest diameter be- 

 ing antero-posterior. The distal end is obUque to the longer axis of the 

 bone, the surface of which looks downward and forward in the articu- 

 lated limb. On the inner anterior face of the distal end a prominent 

 roughened protuberance presents a surface for union with the radius. 



Measurements of ulna. mm. 



Greatest length 263 



Greatest diameter of proximal end 90 



Greatest diameter of distal end 55 



Least diameter of shaft 24 



Radius. — The radius is more slender and somewhat shorter than the 

 ulna. The proximal and distal ends are expanded, more especially 

 the former (fig. 5). In cross-section the shaft is angularly rounded 

 throughout the greater part of its length. The proximal end is 



Fig. 4.— Left ulna of Allos- 



AXIBUS FRAGILIS MaESH. CaT. 



No. 4734, U.S.N.M. i NAT. 



SIZE. POSTEEIOR VIEW. 



Fig. 5.— Right radius of Allo- 



SAURUS FRAGILIS MaRSH. CaT. 



No. 4734, U.S.N.M. J NAT. 

 SIZE. Internal view, d, 

 DISTAL end; p, proximal end. 



