NORTH AMERICA AND THE WEST INDIES 93 



for three years, since the accession date as shown by its number 

 in the register of the British Museum was 1852. Possibly this 

 species was exterminated prior to the final destruction of the 

 Martinique species. 



There is nothing to indicate when the Barbuda musk-rat 

 was living, but probably it disappeared soon after the occupa- 

 tion of the island by Europeans and consequent destruction of 

 cover. Even in Du Tertre's time the musk-rat was not known 

 from any of the other islands, for De Rochefort's assertion 

 that it was one of the five species of mammals native to Tobago 

 may be received with caution. 



MUSKEGET ISLAND BEACH MOUSE 



MICROTUS BREWERI (Baird) 



Arvicola breweri Baird, Mammals North Amer., Pacific Railway Repts., vol. 8, p. 525, 



1857 (Muskeget Island, Massachusetts). 

 FIGS.: Miller, 1896, pi. 1, figs. 1, la (skull). 



The Brewer's beach mouse of Muskeget Island, lying be- 

 tween Marthas Vineyard and Nantucket Island off southeast- 

 ern Massachusetts, is of special interest on account of the 

 characters it has developed of large size and pallid coloration, 

 differing in the latter respect particularly from all the other 

 island meadow mice of our coast. It is generally supposed that 

 these traits have resulted from isolation and inbreeding on the 

 confines of this small sandy island. On the other hand, it may 

 be that the beach mouse is a relict species that was formerly 

 an inhabitant of the now- vanished sandplain, which extended 

 coastwise from New Jersey to Newfoundland, and forms a 

 case parallel with that of the Ipswich sparrow of Sable Island, 

 Nova Scotia, a pallid form of that sandy spot, not found 

 elsewhere at the present day. 



In addition to its somewhat larger size when adult, as com- 

 pared with the common Microtus pennsylvanicus of the neigh- 

 boring mainland and the island of Nantucket, the beach mouse 

 is strikingly pale, a "light gray throughout, purest (almost 

 white) on the belly and tinged with wood-brown on the sides 

 and back, the latter somewhat darkened by a sprinkling of 

 longer blackish hairs . . . Tail indistinctly bicolor, brown- 

 ish dorsally, whitish ventrally" (Miller, 1896). A large per- 

 centage of these mice have a white mark in the forehead. The 



