1911] Taylor: Mammals of the 1909 Xevada Expedition. 233 



vegetation; (5) steep, rocky mountain sides; (6) along moun- 

 tain creeks in dark, damp situations; (7) by fallen trees; (8) in 

 rock-piles; (9) in chinquapin thickets; (10) in sagebrush: (11) 

 in dry leaves in the bottoms of canons; (12) in rocks on the sum- 

 mits of ridges; (13) in the white-bark pine belt, and (14) in the 

 mountain mahoganj^ (Cercocarpus ledifolius) region. 



One female Peromysciis (no. 8028) was parasitized l\v two 

 enormous rabbit-tly larvae, but did not seem to be in poor condi- 

 tion, and was about to give birth to five young. 



Some of these mice were caught in deserted Oregon ground 

 squirrel burrows in a meadow on Big Creek (altitude 7000 feet). 

 Evidently they "jump" abandoned squirrel claims. There is a 

 slight possibility that they are sometimes parasitic upon these 

 squirrels (see Seton. 1909, p. 386). 



That the period of gestation extends over at least several 

 mouths is obvious from an inspection of the tables prepared to 

 exhibit the data obtained. During all the summer months females 

 containing embryos were as likely to be captured as females 

 suckling young. As for the breeding of the species throughout 

 the year (see Osgood, 1909, p. 27), I think it unlikely in northern 

 Nevada, as the extreme cold of the winter probably inhibits sexual 

 activity. It is interesting to note that a large proportion of the 

 sexually active animals obtained were not fully adult, but are 

 more properly to be termed "adolescent," being young of the 

 previous year. 



