AET. 15 ANATOMY OF THE EARED AND EARLESS SEALS — SOWELL 33 



of the length of the arm. From a functional standpoint this is not 

 accurate, as the effective area of the manus in the eared seals is 

 augmented by a considerable cartilagenous extension of the digits. 



The nomenclature of the carpal and tarsal bones herein employed 

 has been adopted after due deliberation, and is made up from the 

 three methods of terminalogy (see, for instance. Flower and Lydek- 

 ker, 1891, pp. 49 and 52) usually used in the cases respectively of the 

 simpler reptiles and amphibians, in mammals in general, and third, 

 human anatomy. Those terms are used which it is felt that the 

 student who has not specialized in anatomy will most readily grasp 

 and remember. The carpal elements, then, consist of scapholunar, 

 ulnare, first, second, and third carpales, unciform and pisiform. 



The proximal articular surfaces of the scapholunar and ulnare, 

 and of the metacarpals of Zalophus extend slightl}'^ farther dorsad 

 than in the Phoca. This, clearly, has been brought about by the usual 

 position of the forefoot when the animal is on land, the otariid rest- 

 ing the anterior portion of the body upon the carpus, with the digits 

 at a right angle to the forearm ; while such a position is more rarely, 

 and perhaps less decidedly, assumed by the Phocidae. In Zcdophus 

 the scapholunar is perhaps of unusual size, largel}^ because of the 

 great distal width of the radius. Carpale 1 is very large, probably 

 not so much because it is primitive (Gregory, 1910) as that it has 

 need to conform in size to the stoutness of the first metacarpal. 

 Carpale 3 is the smallest of this series but is not pyramidal in form, 

 and there is broad contact between the scapholunar and the large 

 unciform. The pisiform occupies the angle between the radius and 

 ulnare. The proximal extremeties of the first four metacarpals are 

 approximately on a line, but that of the fifth is located markedly 

 more proximad, articulating mediad with the unciform and to a 

 very slight extent with the ulnare. The metacarpals do not lap 

 one over the other, but there is an extensive articulation between 

 the heads of the second and third. 



In the Phoca there has been considerable reduction in the size of 

 'the carpus, and alteration in the relationship of the elements so as to 

 allow excessive abduction of the manus. Carpale 1 is moderately 

 large, but perhaps not when one considers the greater robustness of 

 the pollex. The proximal end of the first metacarpal, however, is 

 distad of the level of the middle three; in fact in dorsal view the 

 proximal end of carpale 1 and of metacarpals 2, 3, and 4 are upon 

 the same level. Carpale 1 reaches the scapholunar upon the palmar 

 aspect but not dorsad, for between there is interposed carpale 2, 

 which has broadened and lies between the first carpale and meta- 

 carpus two on the one hand, and the scapholunar upon the other. 

 The second carpale is thus invisible from the palmar aspect; and the 

 unciform is also much smaller from this view than it is dorsad, while 

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