ART. 15 ANATOMY OF THE EAEED AND EARLESS SEALS HOWELL 27 



of prime importance in the modification of the scapula, and the long 

 division in Phoca has not even taken full advantage of the extension 

 of the gleno-vertebral angle. In fact, the rhomboids and serratus 

 magnus, rather than any muscles more intimately of the shoulder 

 girdle or brachium, have been chiefly instrumental in this gleno- 

 vertebral extension. In Phoca the " teres major fossa," occupying 

 the more caudal division of the infraspinous space, is large; in 

 Zalophus it is much smaller and occupied by the origin of the teres 

 minor, while the teres major has been segregated upon the border of 

 the bone adjoining the angle, with limitations well defined osteologi- 

 €ally. Between the teres fossa and the infraspinous fossa proper is 

 Si slight ridge, occupied in Zalophus exclusively by origins of triceps 

 divisions, and in the Phoca by the teres minor also. In neither ani- 

 mal is there a true coracoid, but only a faintly indicated bicipital 

 process upon the cranial margin of the glenoid fossa, from which 

 arises the biceps. The angle of the scapular spine in relation to the 

 glenoid fossa is the same in both. 



Anterior limb. — ^In the Pinnipedia the functional length of the 

 arm is so termed only because I am using this standard of comparison 

 in the investigation of other mammals, and it signifies merely such a 

 standard. Because most of the arm is within the body, and, further- 

 more, because in the Zalophus there are cartilagenous extensions of 

 the digits, this functional arm length, so termed, bears an unknown 

 relation to the etlective lever power of the forelimb, which is dis- 

 cussed elsewhere. This length of arm then, which is of great value 

 from a phylogenetic viewpoint, consists of the distance from the tip 

 (exclusive of the nail in Phoca) of the first digit to the proximal 

 termination of the radius, plus the length of the humerus, from 

 trochlea to head. In the Zalophus^ this comprised 66 and in the 

 Phoca 48 per cent of the body length (82 in a cat) ; or, expressed 

 differently, relative to body length, that of the Phoca was about 72 

 per cent as long as in Zalophus, a disparity still further increased 

 during life by the presence in the otariid of cartilagenous extensions 

 upon the digits. 



Upper arm: Humerus. — In the Zalophus the humerus comprised 

 27, and in the Phoca^ 30 per cent of the arm length (38 in a cat). 

 Because of the disproportionate length of the manus in the former 

 animal this comparison is not as significant as is the humero-radial 

 comparison, which in the otariid was 95 and the phocid 104 per 

 cent. Of the body length the humerus comprised 18 and 14 per cent, 

 respectively (31 in a cat). The articular surfaces of the Zalophus 

 are the more robust, relatively, and the fact that the normal position 



* The manus and pes were disarticulated in the Zalophus skeleton, and the measurements 

 ■computed after reconstruction upon sheets of modeling clay. They were not disarticulated 

 in the Phoca. 



