232 BULLETIN OF THE 



tion, from half-submerged meadows to the driest sandy plains. Dr. 

 Godman, in his American Natural History,* under Arvicola xan- 

 thognathus, has very minutely described the habits of this species. 

 While in meadows it forms roadways among the roots of the grass on 

 the surface, in grain-fields it burrows beneath the surface, its habits 

 varying with circumstances. In the latter situation the vegetation 

 is not generally sufficiently dense to screen it, hence its more sub- 

 terranean mode of life. Their nests are found containing newly 

 born young from early in May till November. The number of litters 

 produced by a single female in- a year is probably generally not less 

 than three, and may be more ; the young of the early litters also them- 

 selves appear to have young the same season ; hence the great rapidity 

 of increase that obtains in this species. 



Specimens, even from the same locality, vary considerably in size, color, 

 the texture of the fur, and even in the shape of the skull, independently of 

 considerable variations that result from age and season. On these variations 

 have heen erected numerous nominal species, some of which are already 

 currently considered as synonymes of A. riparius Ord, and several more, 

 doubtless, should be added to the list. Among those described from or 

 attributed to Massachusetts which I refer to A. riparius are .1. hirsuius 

 and A. albo-rufescens Emmons,f .4. nasuta Audubon and Bachman, J and 

 A. Breweri and A. riifidorsum Baird ;§ also, A. rufescens De Kay, || from 

 New York. 



On Muskeget Island (a small, uninhabited, low sandy island between 

 Nantucket and Martha's Vineyard) I recently found the so-called A. Brew- 

 eri excessively abundant. This is the only locality from which this sup- 

 posed species has been reported. They are generally much paler in color 

 than the A. riparius of the interior, and though not ditfering from them ap- 

 preciably in any other respects, they form an interesting insular race. From 

 the peculiar character of the locality, the scattered beach-grass growing 

 upon it affording but slight protection to these animals from the sunlight, 

 the intensity of which is greatly heightened by the almost bare, light-colored 

 sands, the generally bleached appearance of the Muskeget Arvicola might 

 have been anticipated. Specimens occasionally occur of nearly the ordi- 

 nary color, or which are undistiuguishable from the lighter-colored speci- 



* Vol. H, p. 66. t Report on Quad, of Mass., p. 60. 



| Journ. Phil. Acad. Nat. Sci., Vol. VIII, p. 2U6; Quad. N. Am., Vol. Ill, p. 211, PI. 

 144, Fig. 2. 

 § N. Am. Mam., pp. 525, 526. 

 || N. Y. Fauua, Vol. I, p. 85, pi. XXII, Fig. 1. 



