Mar. 1898. NORTH AMERICAN MAMMALS ELLIOT. 207 



Mount Hamilton, in this collection, the last named locality being 

 one of those from which his typical series came, and I am able 

 to distinguish no characters worthy of consideration to suggest 

 separating them. Some of my examples from those localities 

 were compared with Dr. Merriam's specimens of boy Hi and agreed 

 with them, so they may be considered as typical. The skulls of 

 all these specimens, as may be expected, show considerable 

 individual variations, but there are no characters, in my opinion, 

 to be found among them upon which even a separate subspecific 

 form can be based. After very careful investigation, with proba- 

 bly one of the largest series of this form existing to assist me, I 

 am unable to arrive at any other conclusioi} than that gilberti &&& 

 boylii are the same, and that the former must become a synonym. 

 In his remarks on -S". gilberti Dr. Allen, com pares it with P. cali- 

 fornicus, " in many respects a miniature " of that species. But 

 the two animals do not at all resemble each other, gilberti type 

 being reddish brown, and calif ornic us is never that color, and 

 among the specimens from Stanford University I do not find any 

 ' P. calif ornic us from the localities from which Dr. Allen said his 

 examples came. There is, however, a Peromyscus from Portola 

 which seems not to have been described, and possibly Dr. Allen 

 may have had a representative of it before him among his gil- 

 berti specimens not sufficient to make its differences conspicuous, 

 but which might have led him inadvertently to consider his form 

 comparable with calif ornic its. In this collection there is a series 

 of this mouse which I propose to separate as 



31. Peromyscus dyselius. Sp. nov. 



Twenty-seven specimens all procured at Portola, San Mateo 

 Co., from December to April, the majority in the former month. 

 Similar in color to P. calif ornic its, but very much smaller in 

 size. Top of head, greater part of back and center of rump 

 black interspersed with buff, many hairs being tipped with that 

 color. Rest of head and back of neck grayish-buff, sides pale 

 buff, hairs tipped with blaek and separated from the white of 

 the underparts by a line of bright deep buff. This line extends 

 the entire length of the body onto the shoulders and along the 

 sides of the face to the anterior edge of the eye; a black ring 

 surrounds the eye. Nose, flesh color. Whiskers longer than 

 the head, black and silvery gray. Lips and entire under parts 

 pure white, hairs-plumbeous at base, sometimes a fulvous spot of 

 greater or less extent is present on the breast. Hands and hind 



