MILLER: BEACH MOUSE OF MUSKEGET ISLAND. 85 
ent parts of its range. Very dark specimens come from near the 
southern limit of the animal’s distribution, while a race slightly paler 
than the average occurs along the coast of Massachusetts and on 
the neighboring islands. Of the pale animals from the coast I have 
examined specimens taken at Ipswich (Hog Island), Revere, Ware- 
ham, Provincetown, Monomoy Island, Martha’s Vineyard, and Nan¬ 
tucket. In none of these localities do the mice show any close 
approach to the coloring of the Muskeget mouse or to the peculiar 
harsh, coarse fur of that species. I was unable to find traces of 
voles on the Ipswich sandhills, where Mr. Allen observed that the 
* mice often present . . . the half-white appearance of A. [A/.] 
breweri ,” but on Hog Island, 1 separated from the sandhills by the 
narrow Ipswich River only, they were abundant and in no way 
peculiar. Unfortunately the specimens on which Mr. Allen based 
his statement concerning the color of the Ipswich mice are no longer 
in the Museum of Comparative Zoology. On Monomoy Island, the 
surface of which is exactly like that of the Ipswich sandhills, and 
very slightly, if at all, different from that of Muskeget, Microtus 
pennsylvanicus is common and exactly like the mice occurring else¬ 
where on the Massachusetts coast. Two dozen specimens from 
Martha’s Vineyard and a series of sixty odd from Nantucket show 
that the voles of these islands are identical with those of the adja¬ 
cent mainland and not at all like Microtus breweri. Unfortunately 
the available material from Tuckernuck is insufficient to decide the 
status of the Microtus occurring there. An adult taken on this 
island in June, 1893, is nearly as pale as some of the darker exam¬ 
ples of Microtus breweri , but the skull is so broken as to make 
identification impossible. 
Albinism—perhaps one of the stigmata of degeneration due to 
enforced inbreeding — was very noticeable among the mice on 
South Point Island. Of the forty-three taken on June 21, 1893, no 
less than nineteen were slightly albinistic. 2 Each of these abnormal 
individuals showed a distinct white patch or tuft on the median line 
of the head just back of the eyes. Only one specimen was marked with 
white elsewhere on the body. In this case there was a broad white 
stripe beginning on the lower lip and passing back under the chin 
and throat. It is a significant fact that in everv instance the abnor- 
1 Where, however, the conditions are exactly as on the mainland and not in the least 
as on the sandhills. 
2 Among the 2G specimens collected by Mr. W. K. Fisher in July, 1895,10 are marked 
with white on the head. 
