RODENTIA MURINAE HESPEROMYS GAMBELII. 



Color. Above, mixed glossy brown and yellowish brown, the former predominating on the 

 back. Sides but little paler. Ears dusky. The white of the fore leg extending as far as the 

 elbow. Under parts and feet white. Tail white, dusky above ; the difference of color very 

 evident. 



Several specimens of Hesperomys were caught at Posa Creek by Dr. Heermann, differing in 

 some respects from the others brought in from the west by exploring parties. As they appear 

 not quite grown, I hesitate about describing them as new, and, for the present, at least, prefer 

 to place them under H. gambelii. 



This species differs from H. boylii in the much shorter tail and less number of caudal verte 

 brae, more villose ears, with longer fur at their inner base on the top of the head, shorter hind 

 feet, &c. 



This species, in size and general appearance, represents very closely the Hesperomys leucopusof 

 the eastern States to such a degree, in fact, that as yet I have not found any easily expressed 

 characters to distinguish them. There is the same plumbeous hue in the young, the yellowish 

 brown of the back, &c. I do not find, however, a tendency to a distinct darker stripe on the 

 middle of the back, as in H. leucopus, and the general appearance of a series of each is quite 

 different. It is barely possible that my H. austerus may be a northern variety of the common 

 Californian species, of smaller size and darker color, somewhat like the gray and smaller H. 

 leucopus of Nova Scotia, and probably Labrador. The differences, however, are considerable, 

 and further materials will be necessary to decide the question. 



List of specimens. 



59 L 



Possibly H. boylii. 



