214 Proceedings of the Biological Society of Washington. 



County; 2 skins with skulls from Petaluma, Sonoma County; 1 skull 

 from " Marin County." 



Distribution. — The lowlands of west-central California, particularly the 

 delta region at the confluence of the Sacramento and San Joaquin rivers; 

 west to Petaluma and Marin County. No minks are known to occur 

 on the south side of Golden Gate and San Francisco Bay. 



Remarks.— Th& field has been clarified, nomenclaturally, by Hollister 

 in his Synopsis of the American Minks (Proc. U. S. Nat. Mus., vol. 44, 

 1913, pp. 471-480); there appears to be no obstacle to bestowing a new 

 name upon the race here pointed out. There are doubtless characters 

 pertaining to general size of the animal and to color and quality of pelage, 

 but lack of satisfactory material prevents definite statements regarding 

 them. It is to be expected, from the cranial dimensions, that the Cali- 

 fornia Lowland Mink is of smaller size than its relative, energunienos. 

 The coloration, in corresponding season, is notably pale, as compared 

 with that of the few northern and mountain minks at hand, and there is 

 little or no white on chin and throat. Also the pelage is not so heavy, 

 the overhair in particular seeming more scanty. 



The localities in California, from which there are specimens in the 

 Museum at this time referred to energumenos, are: Jackson Lake, 

 Siskiyou County, 1; North Fork CofTee Creek, Trinity County, 1; Hay 

 Fork, Trinity County, 3; Cuddeback, Humboldt County, 3; Carlotta, 

 Humboldt County, 4; Independence Lake, Nevada County, 6; Cisco, 

 Placer County, 1; Merced Lake, Mariposa County, 3; Fish Springs, Inyo 

 County, 3. 



Measurements, in Millimeters, of Skulls of Adult Males of Mustela 

 vison aestuarina, All From West-central California. 



* Measured from anteriormost projection of premaxillaries to posterionnost vertical 

 plane touching both occipital condyles. 



t Measured by placing calipers at least width of brain-case in front of mastoid 

 processes and behind posterior zygomatic roots. 



X Measured at narrowest part of rostrum behind bulging bases of canines. 



S'iType. 



