94 EXTINCT AND VANISHING MAMMALS 



skull in adults is larger than that of typical M. pennsylvanicus, 

 with somewhat longer and narrower brain case, more abruptly 

 flaring zygomatic arches, and the outline of the interparietal 

 is longer and narrower. Average adult length, about 200 mm. 

 (8 inches). 



Muskeget is distant only 6 miles from the western end of 

 Nantucket. The intervening waters are shallow and on the 

 south side it is partly protected by some small islands and long 

 beaches. In his account of this mouse and its island, Miller 

 (1896) writes that in 1887 the United States Coast Survey 

 found the southern point extending out much farther to the 

 southwest than in later years, during which the sea washed 

 away all but the tip of the point, which remained as South 

 Point Island. He found about a dozen species of birds breeding 

 there and the white-footed mouse occurred in the clumps of 

 beach plum, or about the numerous small houses along the 

 south shore of the island. The beach mice seem to have had 

 various ups and downs. In 1869 they were recorded as "exces- 

 sively abundant"; in 1890, however, only a few were found by 

 two naturalists visiting the island, while in 1891, William 

 Brewster was unable to find any trace of them. Miller records 

 that the warden, Mr. Sandsbury, who was stationed there in 

 summer to protect the tern colony and who had been familiar 

 with the mice for many years, believes that they had actually 

 been exterminated by cats that ran wild on the island after the 

 burning of the Life Saving Station a few years before. Since 

 the mice can burrow but little in the loose sand, they may 

 have been the more easily exterminated in this way. When 

 Miller visited the locality in 1892, he found, however, that 

 there were large and thriving colonies on South Point Island 

 and the adjacent Adams Island, which had been cut off from 

 Muskeget previous to the burning of the Life Saving Station. 

 This accident had therefore saved the mice from total extinc- 

 tion. Of the further history of this interesting population, 

 Miller (1896) writes: "The 28th of December, 1892, I spent 

 on Muskeget and the neighboring islands. The mice were as 

 numerous as before on South Point Island, but the colony on 

 Adams Island had greatly diminished. In June, 1893, I again 

 visited Muskeget, this time in company with Mr. Outram 

 Bangs and Mr. Chas. F. Batchelder. We found that the 

 Microtus colony on Adams Island had entirely disappeared. 



