4 PEOCEEDINGS OF THE NATIONAL MUSEUM vol. 73 



to be held within the body contour and virtually immovable, the only 

 way that the foot can assume the plantigrade position used in walk- 

 ing is for the sacral vertebrae to be forced into a position that is 

 practically vertical to the ground, which is done with ease. The 

 hind limbs apparently play a much less important part in swimming 

 than one would infer from the degree of specialization which they 

 exhibit. 



The Phoca hispida, as typifying the earless seals or phocids, is 

 really a very different animal. It, too, is stream line in form but in a 

 somewhat different manner from the otariid. Usually fat, it is of 

 greater circumference than the otariid of the same mass, excepting 

 adult bulls of the latter, and in most forms at least is relatively 

 shorter. The shortness of the neck seems especially marked and to a 

 greater degree than is actually the case, for it is very wide, tapering 

 to the broad thorax. The neck is not markedly flexible, as is that of 

 the otariid — in fact, it is probably less so than in the average fissiped, 

 and one gains the impression that the entire trunk is less agile than 

 in the sea lion. The forelimbs are weak, are not used as a primary 

 means of propulsion through the water but in lateral, water-treading 

 movements, and their use on land is limited to such acts as aiding in 

 the surmounting of a low obstruction. Swimming is accomplished 

 by a rhythmic, transverse movement of the hind feet, presented palm 

 to palm, the moA^ements being on the whole comparable to those of a 

 fish in swinmiing. Both otariids and phocids may swim for con- 

 siderable distances on the back, but the former assumes this position 

 evidently for brief periods only, while the latter is more prone to 

 do so, at least in captivity. For several anatomical reasons, as dis- 

 cussed later, the Phocidae can not place the hind foot to the ground 

 in a plantigrade manner and apparently never attempt to do any- 

 thing with the feet while on land save keep them, palm to palm, 

 elevated well out of harm's way. Terrestrial progression is accom- 

 plished by a caterpillarlike wriggling in the sagittal plane — not in 

 the horizontal or transverse one — with the forefeet close to the sides 

 and the hind ones elevated above the ground. 



MATERIAL 



The material assembled for the present work was not all that was 

 desired but was the best that could be procured. As representing 

 the Phocidae an embalmed subadult female of Phoca hispida taken 

 by H. C. Raven, Ponds Inlet, Baffin Island, August 30, 1926, was 

 obtained by exchange from the American Museum of Natural His- 

 tory. But a single skeleton, partially articulated, of this species 

 could be located and that was borrowed from the Museum of Com- 

 parative Zoology through the courtesy of G. M. Allen. It is of a 



