228 Uinvo-silij of ('alifor)iia Puhlications in Zoology. [Vol. 7 



Onychomys brevicaudus C. H. Merriain 

 Short-tailed Grasshopper blouse. 



The only individual of this species taken was an adult female 

 (no. 7883), trapped June 10 at Big Creek Ranch near a brushy 

 plant on the desert. Compared with the specimens of Onychomys 

 in the ^Iiiseum collection and with the original description of 

 brevicaudus, the specimen seems referable to that species. It 

 measures, total length, 138 mm.; tail vertebrae, 40; hind foot, 19. 



This mouse was described (C. H. Merriam, 1891, p. 52) from 

 Blackfoot, Bingham County, Idaho. Bailey (1908, p. 13) asserts 

 its abundance throughout the sage-brush valleys of the Great 

 Basin country. In our experience it is one of the rarer mammals. 



Peromyscus maniculatus sonoriensis (LeConte). 

 White-footed jMouse. 



Status. — As would be expected from geographic considera- 

 tions (see Osgood, 1909, pi. I, frontispiece), our series of 120 

 short-tailed Po-omyscus is unquestionably referable to sonor- 

 ioisis. The specimens accord well with Osgood's characterization 

 (1909, p. 89). 



"Barriers impassable to many other mammals have little effect 

 on these mice, for they range continuously although not always 

 without undergoing change from sea-level to great altitudes, and 

 from the very humid to the very arid regions." (See Osgood, 

 1909, p. 17). In order to ascertain whether examples of the 

 species from the highest parts of the Pine Forest Mountains 

 would show any tendency to vary from the mode of specimens 

 from the desert Hat, I selected representative adults from various 

 localities and tabulated the external and cranial measurements. 

 The adults were selected on the basis of skull characters mainly, 

 stage of tooth-wear being the most important. In the table only 

 the very old adults are included. 



It will he seen that llic differences shown are very slight. 

 There does seem to be a tendency in the white- footed mice of the 

 mountains to be slightly smaller than those from the plains. This 



