MURID2E— ARVICOLIN.E— CUNICDLUS 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 ihe 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. At, 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 (ohensis). 

 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 "a 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. Grcenlandicus 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 



