MURIDA—ARVICOLINAZ—CUNICULUS TORQUATUS. 249 
ening from the base, when it appears like an excrescence; it is finally lost. 
Thus the process appears to be a periodical one, like the shedding of the 
horns of ruminants, and not continually progressive with age; and would 
seem to be connected with the particularly fossorial habits of the quasi-hiber- 
nating animal that digs galleries under ground in which to reside during the 
cold season, as compared with its freer and more active mode of life in 
summer. At the period of the maximum development of the claws, these 
equal or surpass half an inch in length, and yet the hairs upon the dorsum 
of the fore feet reach to or even beyond their tips. Af the same season, the 
hairs upon the hind feet form a fringe drooping far beyond the ends of the 
claws, and the terminal pencil of hairs on the tail is almost invariably longer 
than the vertebral portion. The winter-coat is much longer and thicker than 
that of summer; the difference is well shown in those intermediate speci- 
mens that are white and woolly, yet with definite stripes of shorter, thinner, 
colored hairs. 
Audubon’s plate of the summer pelage is highly erroneous, representing 
a uniformly rusty-red animal instead of a dappled and otherwise variegated 
one. The coloration as given is, in fact, exactly as in Myodes helvolus (obensis). 
whereas the two are distinguishable on sight by color alone. His figure of 
the winter pelage is very good, representing, however, an animal not perfectly 
white. 
There is no question of the identity of the American and Asiatic animal. 
In an abstract of the present memoir, already published in the Proceed- 
ings of the Philadelphia Academy, we cited Forster as authority for the name 
Mus hudsonius, quoting at second hand, the volume of the Philosophical 
Transactions not being conveniently accessible at the time. On turning to 
the page indicated, we find that Forster gives no such name; he merely 
describes a mutilated specimen from Churchill River, of ‘fa small animal 
called a Field Mouse” Pallas is the author of the name Mus hudsonius, at 
date 1778; but it is “‘antedated” by the same author’s Mus torquatus, 
described on preceding pages of the same work. The species will conse- 
quently stand as Cuniculus torquatus. Mus lenensis Pallas is the same animal, 
of same date. Grenlandicus and ungulatus are later names of nominal 
species. 
The following table of measurements of our excellent series shows the 
size and, to a considerable extent, the variations of the species, but does not 
