OSTEOLOGY OF CAKNIVOKOUS DINOSAURS. 59 



articulated radius and ulna well out away from the body. The deltoid or radial 

 crest is strongly developed, as a short but high thin plate of bone, that is situated 

 on the anterior-external border immediately above the middle of the shaft. Viewed 

 from the front it renders the anterior surface deeply concave transversely (fig. 41). 

 Below thi§ crest the shaft is constricted and angularly rounded in cross section. 

 The head is situated in about the middle of the proximal end with the articular 

 portion overhanging the posterior surface of the shaft. The radial and ulnar con- 

 dyles are well defined. Posteriorly they are separated by an unusually broad but 

 shallow depression which continues somewhat upward on the shaft of the bone. 

 The articular ends of the humerus are rugosely roughened. A prominent rough- 

 ened oval shaped area on the postero- 

 external surface at the lower border of "^ ^ ^ 

 the radial crest, probably represents the 



•point of insertion for the humero-radi- y" , r^^^ 'v-mW///////^ 



alls muscle (pi. 6, figs. 2 and 4). The / ^^'^^0% jwif '"^ 



measurements given below were made '" / / Vwm 



from the humerus of the right side, which > n i/ 1 ^// 



is the better preserved of the two: , ^ rtJii ■^'" T w "' 



Measurements of humerus of Anlwdemus vttlens. \ 'B™! I "Im/'f 



mm. \ 11 



Greatest length 310 1 ' 



Greatest width of proximal end 118 \ ' 



Greatest width of distal end 100 l 



Least diameter of shaft 38 J, Ln,,,,,,,,,, ,,, . 



Ulna (u). — ^T'he ulna is expanded and 



heavy proximally with a less expanded ,,„. ., 



distal end. It exceeds the radius in ^ ^, || /''t'' 



length but is shorter than the humerus. ^i'M'i' * /,iiill L ' ""' 



The proportion bemg as 1 : :1.1 7. \\'- im 



There is a heavy olecranon process (o. ^^-"ms^^, \^/!P \- j- 



fig. 42) that extends considerably above xB^ XaX ""• 



the articular surface for the humerus. ^^^ 4i.-right humerus of anLdemus valens le.dv. 



The surface of this process is roughened cat. no. 4734. u.s.n.m. jnat. size, ^.posterior view; 



f^ ,„, ,„„,,!„« ;,-.„.^„+;„„ TU^ 1„ B. anterior view; A. head; r.c. , RADIAL CREST; i.e.. inner 



for muscular msertion. The olecranon ,„^„^,^. „^ <,^,,^ ,„^„.,^ 



process is less well developed in Ceratosau- 



rus nasicornis and appears to be entirely wanting on the ulna of Ornitholestes her- 



manni, though robust in Ornithomimus. 



The articular surface for the humerus is comparatively narrow transversely, 

 with a shallow concave surface antero-posteriorly. The concavity on the proximal 

 end for the reception of the head of the radius is shallow. The shaft of the ulna is 

 slender, suboval in cross section, and in a distal direction, gradually expanding 

 into a moderately large end, the greatest diameter being antero-posteriorly. The 

 distal end is oblique to the longer axis of the bone, the surface of which looks down- 

 ward and forward in the articulated limb. On the inner anterior face of the distal 

 end, a prominent roughened protubrance presents a surface for union vvith the 

 radius. 



