480 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. 
In the sea-lions (fig. 8) the fore limbs are the sole organs of locomo- 
tion, while the hind flippers serve only for steering; exactly the oppo- 
site, therefore, of the seals. The fore feet are large and long and in 
form remind one of the wings of penguins and auks. They have not 
Fig. 7.—A seal in a swimming posture. (After P. Gervais.) The first and fifth toes 
of the hind feet are of equal length; the middle toe is the shortest. The hind flippers 
are contracted and therefore in the position they assume after a back stroke. The 
fore ilippers serve only for steering. 
the slightest similarity with those of whales and sea-cows. In swim- 
ming, they are turned about in a peculiar fashion like a screw. 
The walrus moves in the water in such a manner that both fore and 
hind flippers serve in locomotion. The fore flippers move alternately, 
as in sea-hons 
and turtles. The 
hind flippers, on 
the contrary, are 
turned about in 
the same manner 
as in seals. The 
swimming mo- 
tion of the walrus 
is, therefore, en- 
tirely different 
from that of the 
Fic. 8.—Hared seal lying on land. (After W. Haacke.) The fore . 
limbs, which serve as propellers, are formed like the wings of sea - lions an d 
penguins, seals. 
The tail is rudimentary in all three families of pinnipeds, and plays 
no role in locomotion. 
The dentition of the seals is simplified. It serves for masticating 
food only in the walrus. In all other pinnipeds, it serves for grasp- 
ing. Speaking generally, the molar teeth of the seal are serrate, with 
sharp cutting cusps, while those of the eared seal are single-pointed 
