DR. J. MURIE ON THE ANATOMY OF THE WALRUS. 495 
The tail in the Walrus reaches only to the heel. In the Seal it projects considerably 
beyond it, even as much as 4 or 5 inches. 
The free membrane joining the tail to the limb reaches no further than the os calcis 
in the Walrus, and the foot then can be turned at a right angle to the heel. In the 
Seal the same caudal expansion or sheet of integument reaches considerably beyond the 
os calcis, as far even as the proximal end of the metatarsals. 'The membrane likewise 
goes towards the middle of the foot, in this manner binding the soles together, so that 
when these are expanded they face each other and prevent all movement of a planti- 
grade kind. 
It is thus with difficulty the two hind feet can be dragged out at right angles with 
the body, the natural movement being a kind of sculling one towards each other, the 
soles facing one another mesially. 
The hind foot in the Walrus is in some respects like that of the Sea-lion, both, for 
instance, in its manner of attachment and in the movements of the parts one on the 
other. 
In them the caudo-limb membrane only extending to the heel allows great laxity of 
movement. Besides rotation, pronation, and supination, the feet can be thrust back- 
wards in the long diameter of the body, somewhat in the same manner as obtains in the 
common Seal. 
The hind foot (pes) in the Walrus, as previously stated, can be twisted forwards and 
used as a support in walking, similar to the method of progression of the Sea-lion ; 
nevertheless there is noticeable a slight difference in the mode of action. The Walrus 
is often seen to thrust its toes more below the belly, whereas the Sea-lion drags them 
flappingly outwards, and its great long toes at times even overlap or strike against the 
fore limbs. This latter was not observed in the Walrus, the toes appearing to be 
shorter and less rigid. 
The nails on the pelvic limb of the Walrus are larger than those of the fore foot. 
The sole is bare and the dorsum covered with short hairs as far on as the proximal 
phalanges. 
The development and disposition of the nails of the hind limb is a very trenchant 
character, distinguishing the three genera of Pinnipedia already so often referred to. 
In Trichechus they are altogether diminutive, subequal in size, and, from the short distal 
phalangeal cartilages, moderately, and indeed the three median ones rather, near the 
toe-tips. In Otaria the two outer ones are but rudiments, whereas the three mesial 
ones are large and strong: they are placed at a considerable distance from the points of 
the digits. In Phoca the nails assume a claw-like size and figure, are situated quite at 
the digital extremities. and the middle three are much smaller than the outer two. 
