274 Vnivcrsify of ('nlifor)iia Puhlications i)i Zoolog)). [Vol.7 



The table shows that there is difference in size between our 

 specimen and si»iioh(s. The dorsal and ventral tail stripes of 

 the Nevada specimen are very much lighter than the correspond- 

 ing ones of the topotype series of siniioli(s, which present a dusky 

 coloration. 



Although the skull of the Nevada Dipodomys resembles that 

 of simiolus in a general way, it is smaller, has a slightly different 

 shape, and presents several lesser differences. The articular 

 process of the mandible is, for example, much narrower. 



The species must be rather rare in the region explored, as we 

 carried on systematic trapping in localities apparently in every 

 way favorable for its habitation. The specimen secured was 

 caught in a trap set near a small bush on the open desert. 



Perognathus parvus olivaceus C. H. ]\Ierriam. 

 Great Basin Pocket ]\Iouse. 



Status. — As might be anticipated from geographical consid- 

 erations our series proves to be referable to this species. Com- 

 pared with Osgood's description of olivaceus (1900, p. 37) our 

 specimens have the lateral line varying in shade, but more pinkish 

 buff than cinnamon buff. The coloration dorsally is variable, 

 most of the series being buffy, but some presenting a dark grayish 

 tone. The difference between the two types of coloration is not 

 great enough to justify the statement that there are two color 

 phases, and apparently is due merely to individual variation, as 

 it is impossible to correlate the types of coloration with age, sex, 

 or locality. Specimens intermediate between the two extremes 

 are present. The subauricular spot is conspicuous in only about 

 twenty-five per cent, of the series. Of thirty-two specimens, only 

 two (nos. 8125, 8131), have buffy-tipped belly hairs with ])lum- 

 beous bases. One juvenal (no. 8114) has buffy-ti])ped hairs vcn- 

 trally, but their bases are not plunibeous. The inner side of fore 

 leg is white except in four specimens (nos. 8125, 8137, 8134, 

 8122). 



As regards size, the Humboldt C(mnty animals average 

 smaller than the type specimen of olivaceus, but accord fairly 

 well with the averages as given by Osgood. 



