Vol. XXIX, pp. 213-214 September 22, 1916 



PROCEEDINGS 



OF THK 



BIOLOGICAL SOCIETY OF WASHINGTON 



THE CALIFORNIA LOWLAND MINK A DISTINCT RACE. 



BY JOSEPH GRINNELL. 



(Contribution from tlie Museum of Vertebrate Zoology, University of California.) 



There are now eighty mink skulls in the Museum of Verte- 

 brate Zoology taken within the State of California. Some of 

 these are accompanied by skins and a lesser number by complete 

 skeletons; but so far as the present study is concerned, the 

 skulls only are of importance. Recent opportunity has been 

 afforded the writer of comparing selected specimens from Cali- 

 fornia with near-topotypes of Mustela vison energumenos, in the 

 United States Biological Survey and National Museum collec- 

 tions, from Chilliwack, Port Moody and Sumas, British Colum- 

 bia. It has become apparent that there are two races of the 

 mink in California, energumenos (or something very nearly akin 

 to that race), and a distinct one, which is herewith described. 

 A large series of the latter gathered from one locality, Stockton, 

 serves to accentuate the diagnostic characters by its uniformity 

 in mass effect. 



Mustela vison aestuarina new subspecies. 



CALIFORNIA LOWLAND MINK. 



Type. — Male adult comprising skin, skull and body skeleton ; No. 23,660, 

 Mus. Vert. Zool. ; Grizzly Island, Solano County, California, November 

 30, 1915; trapped by A. H. Luscomb for Miss Annie M. Alexander and 

 by her pre.<ented to the Museum of Vertebrate Zoology. 



Diagnosis. — Similar to Mustela vison energumenos, but with cranium 

 lighter in build, rostrum weaker, brain-case narrower and proportionately 

 higher, zygomata less widely spreading posteriorly, and auditory bullae 

 having steeper medial sides. 



Material. — Forty-seven skulls from vicinity of Stockton, San Joa- 

 quin County; 4 skins with skulls and skeletons from Grizzly Island, 

 Solano County ; 1 skin with skull and skeleton from Joyce Island, Solano 



37— Proc. Bioi,. Soc. Wash., Vol. XXIX, 1916. (213) 



