OSTEOLOGY OF ANTARCTIC SEALS. 195 



notch at its base 18 mm. The ventral surface showed a slight subscapular angle cor- 

 responding in position to the attachment of the spinous process on the dorsal surface. 

 Two faint muscular ridges were present, directed towards the glenoid fossa. The 

 glenoid fossa was pear-shaped, deeply concave, with a prominent margin. 



Index. 



Ross seal . . . . .85 



Weddell seal ..... 82-14 



In the leopard seal the epiphysis of the posterior angle was wanting, hence the 

 index could not be ascertained. 



The humerus measured 115 mm. long. The head was convex, and its articular 

 surface was continued forwards on to the base of the lesser tuberosity, which was 

 equally as prominent as the greater one. The shaft was slightly twisted, and pre- 

 sented a strongly marked deltoid ridge. The bicipital groove was in the form of a 

 shallow groove. The lower end presented a well-marked trochlea for the ulna, a slight 

 coronoid fossa, but no radial or olecranon fossae. The capitellum was circular and 

 convex. The internal condyle was more pronounced that the external, the external 

 supra-con dyloid ridge more so than the internal, which did not possess a supra - 

 condyloid foramen or even a process. 



Bones of Forearm. 



In neither were the distal epiphyses fused with the shaft. The ulna measured 

 152 mm. and was expanded above from before backwards so as to form a long but 

 narrow olecranon process. A coronoid process was not present. The articular surface 

 for humerus was concavo-convex, while the facet for radius above was flat and con- 

 tinuous with that for the humerus. The shaft was flat, with a rounded anterior border 

 and a sharp posterior border. The lower end was conical and articulated with radius 

 slightly, and with cuneiform and pisiform. The radius was 135 mm. long. The head 

 possessed a deep cup-shaped cavity for articulation with the capitellum of humerus, 

 while the margin of the head was non-articular except on its inner side, where there 

 was a well-marked facet for articulation with the ulna. On the neck a faint tubercle 

 was noticed, while the shaft was paddle -shaped, with a definite roughness on its outer 

 aspect for pronator radii teres. The lower end was grooved on its posterior aspect, and 

 articulated with the ulna and scapholunar. 



Humero-Radial Index. 



Length of radius x 100 

 Length of humerus 



Ross Seal. Sea Leopard. Weddell Seal. 



117-4 107-1 98-1 



TRANS. ROY. SOC. EDIN., VOL. XLVII. PART I. (NO. 8). 29 



