506 



PROCEEDINGS OF THE NATIONAL MU8EVM. 



VOL. 49. 



sents a thin flattened edge, the anterior edge graduaUy thickening 

 toward the inferior border. 



Measurements of coracoid. 



mtn 



Greatest length at center 120 



Greatest depth at center 170 



Humerus. — Comparatively the humerus of AUosaurus is short and 

 somewhat sigmoid in form. The shaft is hollow, as are all of the 

 limb and foot bones of this genus. Planes passed through the 



greatest diameters of the 

 articular ends would cut 

 one another at an angle of 

 50°. This unusual angu- 

 lation throws the articu- 

 lated 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 bor- 

 der immediately above the 

 middle of the shaft. Viewed 

 from the front it renders 

 the anterior surface deeply 

 concave transversely (fig. 

 3). Below this crest the 

 shaft is constricted and an- 

 gularly rounded in cross- 

 section. The head is situ- 

 ated in about the middle 

 of the proximal end with 

 the articular portion over- 

 hangmg the posterior sur- 

 face of the shaft. The radial and ulnar condyles 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 roughened oval-shaped area on the posterior-external 

 surface at the lower border of the radial crest probably represents 

 the point of insertion for the humero-radialis muscle (fig. 2) . The 

 measurements given below were made from the humerus of the right 

 side, which is the better preserved of the two : 



O.C. 



Fig. 3.— Right humerus of Allosaueus feagilis Maesh. 

 Cat. No. 4734, U.S.N.M. J nat. size, o, back view; 

 b, FEONT view; ft, head; t,c., eadial cbest; t. c, innee 

 condyle; 0. c, outer condyle. 



