MAMMALIA. 433 
In removing the walruses from the seals, to bring them near the pachy- 
derms, we agree with the views brought forth a year ago by a most skilful 
American anatomist (Proceedings of the Boston Society of Natural History, 
III. 1850, p. 242). 
Sirenidia and Walrus together undoubtedly belong to that great group 
called Pachydermata, but do not constitute a single series. The pachy- 
derms need to be revised carefully, and the numerous extinct genera once 
more compared with both the aquatic and terrestrial living types. 
Fam. TRICHECHID# is the only one of the group, and contains but one 
single genus, the genus Z’richechus, composed only of one well ascertained 
species, 7. rosmarus (pl. 114, fig. 8), of the history of which the following 
is an extract from Bell’s History of the British Quadrupeds :— 
“The form of this animal is extremely unwieldy ; its bulk, in comparison 
with its length, being greater than in any other form of Phocide. This, 
with the relative small size of the head, the full, thick muzzle, and the long 
tusks, directed downwards, gives it a most strange appearance. Like the 
seals, it frequents principally the northern regions, where multitudes of 
them associate in herds on the rocks or ice fields, throwing themselves off 
on the first approach of danger into the sea, where they are as active and 
as much at home as the seals themselves. The walrus, however, from the 
form and structure of its teeth, cannot live upon fish to the exclusion of 
vegetable food. ‘The small number of grinding teeth, and more especially 
their extreme shortness and rounded form, are calculated rather to bruise 
the half pulpy mass of marine vegetables, than to hold and pierce the 
slippery hardness of the fish’s scaly cuirass. One of the most remarkable 
peculiarities is the form and size of the superior canine teeth, which are 
directed downwards, and are extremely long and powerful, constituting a 
pair of defences of immense strength. 
“The walrus is found only in the colder regions; it comes often on 
shores or on the ice, and remains there sometimes in herds of forty, eighty, 
a hundred or more, for days together, until they are driven to the sea either 
by alarm or hunger. They are often killed on land at Spitzbergen and 
other northern coasts, by means of a lance or spear, for the sake of their 
oil, and the ivory of their tusks, which is much more valuable than that of 
the elephant, on account of its superior whiteness, and density. Of late 
years, the pursuit of these animals has greatly diminished their numbers, or 
at least taught them more caution, and rendered them extremely fearful of 
their arch-enemy. In the water, the chase of the walrus is exceedingly 
difficult. The extreme thickness and hardness of their skin render it 
impervious even to the stroke of the harpoon, nnleys well directed and sent 
with great force. 
‘Before the persecution above alluded to had taught them to be appre- 
hensive of the approach of mankind, they were often found at a considerable 
distance from the sea; and as the hunters placed themselves between them 
and the water, numbers were intercepted in their retreat, and readily 
destroyed. Of the carcases of the first that fell the hunters made a sort of 
barrier to oppose the remainder; and i in this way, on some occasions, three 
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