96 EXTINCT AND VANISHING MAMMALS 



make these short tunnels with the sole object of reaching the 

 soft parts of the beach grass stems. They are in no way con- 

 nected with the nesting burrows. Another means of shelter is, 

 so far as I know, peculiar to the Muskeget mice. They con- 

 struct frail nests or forms which may be seen scattered about 

 everywhere. The forms are usually open at the top and made 

 of the finer shreds torn off from the beach grass. Each is 

 large enough to contain one animal only. The walls are much 

 thinner than those of the breeding nests, being a mere film of 

 grass fiber, through which the occupant can be distinctly seen. 

 The forms may be built on the bare sand or under some shelter 

 indifferently. Often one partly arches a beaten path. 



"The breeding nests, which resemble those of Microtus 

 pennsylvanicus, are sometimes made under the protecting 

 stalks of the luxuriant Solidago sempervirens or under cover 

 of a fragment of wreckage. When no such convenient shelter 

 can be found the mice construct short nesting burrows. These 

 are from one to two feet in length and penetrate the sand at an 

 angle of about 45. In this way the tunnel descends quickly 

 through the dry crumbling sand at the surface to the more 

 compact layers beneath, where the walls are less likely to cave 

 in and smother the helpless young. At the end of the tunnel is 

 a hollow, completely filled by the bulky nest . . . Four or 

 five young is the usual number in a litter . . . The food 

 of Microtus breweri consists chiefly of the tender bases of the 

 beach grass stalks ... As the supply of Ammophila on 

 Muskeget is practically unlimited the beach mice never suffer 

 from hunger, but the struggle for existence must be fierce, 

 notwithstanding, for few small mammals live in as exposed 

 situations." 



DESERT VOLE; AMARGOSA MEADOW MOUSE 



MICROTUS CALIFORNICUS SCIRPENSIS Bailey 



Microtus scirpensis Bailey, North Amer. Fauna, no. 17, p. 38, 1900 ("Amargosa 

 River, near Nevada line, Inyo County, California"). 



This is a desert-living race of the widespread M. calif ornicus, 

 from which it differs in being slightly brighter in color, a pallid 

 neutral gray above, but not so black as in the neighboring race 

 mariposa of the western foothill belt of the Sierra Nevada; 

 belly smoky gray; tail indistinctly bicolor, brown above, gray- 



