46 THE VOYAGE OF H.M.S. CHALLENGE!;. 



vertically on the outer side of the deltoid ridge, which was not the case in Macrorhinus. 

 In Arctocephalus gazella the humerus was 156 mm. long. The epiphysis of the head 

 was conjoined with that of the greater tuberosity, but that for the lesser tuberosity 

 was distinct. The epiphysis for the inner condyle was distinct from that for the 

 radio-ulnar articular surface. Neither species possessed a supracondyloid foramen. 



The radius and ulna had the characteristic general shape and relative position 

 customary in the seals. The radius had a strong ridge on its anterior border for the 

 pronator teres, its lower end was grooved on the dorsal aspect for the extensor tendons, 

 and immediately below the neck was a low bicipital tuberosity. The olecranon and 

 upper half of the shaft of the ulna were distinctly grooved both on the dorsal and 

 palmar surfaces ; that on the dorsal surface was divided into two unequal parts by a 

 longitudinal ridge which commenced in a tubercle at the free edge of the olecranon. 

 Another tubercle was situated at the anterior end of the same border of the olecranon, 

 and a third at the posterior end. To these parts the triceps and dorsi-ejjitroehlear 

 muscles were attached. The interosseous interval was narrow. The radius articulated 

 at its lower end with the ulna, scapholunar, and cuneiform ; the ulna with the radius, 

 cuneiform, and pisiform. The radius in the adult male was 182 mm. long,, the ulna 

 224 mm. In Arctocephalus gazella they were similar in shape but smaller ; the 

 radius was 152 mm., the ulna 191 mm. long, and the epiphyses were not ankylosed. 



Manus. — There were seven carpal bones. The scapholunar was large and trans- 

 versely elongated ; it articulated with the radius, cuneiform, and the four bones of the 

 distal row. The cuneiform was elongated in the dorsi-palmar diameter and articulated 

 with the radius, ulna, pisiform, scapholunar, unciform, and 5th metacarpal. The 

 pisiform was elongated for 21 mm., and projected inwards from the lower end of the 

 ulna, with which and the cuneiform it articulated. The trapezium, though much 

 smaller than the scapholunar, was next to it in size ; it articulated with it and with the 

 trapezoid and 1st and 2nd metacarpals. The trapezoid was wedged in between the 

 trapezium and magnum, and articulated with them and with the scajmolunar and 2nd 

 metacarpal. The os magnum was a comparatively small bone : it articulated with the 

 3rd metacarpal, trapezoid, unciform, and scapholunar. The unciform, as in the other 

 seals described, did not reach the inner border of the carpus, owing to the articu- 

 lation of the 5th metacarpal with the cuneiform ; it articulated with the 4th and 5th 

 metacarpal, cuneiform, scapholunar, and magnum. All the carpalia were rough on the 

 palmar and dorsal surfaces for the attachment of ligaments, and only the scapholunar 

 had a process, and that a low one, projecting from the inner side of its palmar surface. 



There were five digits, which diminished in length from the pollex to the minimus. 

 The three segments of the pollex measured collectively 241 mm., they were not only 

 longer than the corresponding bones of the other digits but they were broader and 

 stronger. The metacarpal of the pollex, 110 mm. long, was flattened at its carpal end, 



