1918] Kellogg: Microtus calif ornicus Group of Meadow Mice 15 



Microtus californicus aestuarinus, new subspecies 

 Tule Meadow Mouse 



Arvicola montana, Baird (1857, p. 530), part. Petaluma. 



Arvicola (Myonomes) riparius, Coues and Alleu (1877, pp. 156-157, 173, 



178), part. 

 (Microtus) montanus, Trouessart (1898-1899, p. 563), part. 

 Microtus californicus, of some authors, part. 

 Microtus edax, of authors, part. 



Type specimens. — Female adult ; no. 18699, Mus. Vert. Zool. ; 

 Grizzly Island, Solano County, California ; September 8, 1912 ; col-, 

 lected by Annie M. Alexander ; original no. 1942. 



Range. — San Joaquin and Sacramento River valleys, from Tulare 

 Lake, Kings County, north to Chico, Butte County, and east to near 

 Gait, in San Joaquin County ; also west along nortli side of San Fran- 

 cisco Bay to Bolinas, Marin County. Vertical range from sea level 

 up to hardly 500 feet ; zonal range Lower and Upper Sonoran. 

 (See map.) 



Total number of specimens examined, 155, from the following 

 localities in California. Merced County: Snelling, 10; mesa 1 mile 

 N Snelling, 1. Stanislaus County: La Grange, 6. San Joaquin 

 County: Tracy Lake (6 miles SW Gait), 28; Tracy, 1. Solano 

 County : Grizzly Island, 51 ; Cordelia, 3. Sonoma County : Petaluma, 

 10. Marin County : Bolinas, 2. Yolo County : Rumsey, 1 ; Grand 

 Island (2 miles N Knights Landing), 5; Vacaville, 11. Sutter 

 County: Marysville Buttes (3 miles NW Sutter), 12; Butte Slough 

 (1 mile NW Butte), 1. Butte County: Chambers Ravine (4 miles 

 N Oroville), 3; Butte Creek (4 miles SE Chico), 5. Tehama County: 

 Mill Creek (2 miles NE Tehama), 5. (Specimens from Snelling are 

 intergrades between mariposae and aestiiamius.) 



Diagnosis. — Size large (hind foot, 22 to 26 mm., condylobasal 

 length of skull in largest individuals, 31.4 mm.) ; second upper molar 

 normally with an open posterior internal loop (triangle) ; skull long, 

 angular, and much ridged in adults (ratio of zygomatic breadth to 

 condylobasal length about 59%) ; the ridges strongly converging in 

 interorbital region, but always with definite sulcus between them; 

 pelage long and coarse, usually blackish ; feet large ; hip glands 

 present in adult males but rudimentary. 



Color. — General hue of dorsal area much darker than in califor- 

 nicus, the exact shade near Front's brown, but with an evident black- 

 ish cast ; mid-dorsum usually overlaid with long glossy black overhairs. 

 In fresh pelage: Ground color of upperparts approaching sayal 

 brown, but light tipped portions of hairs often almost cinnamon buff ; 

 basal portions of hairs slate black. Long overhairs ranging from dark 

 aniline black to black. Color of upperparts shading into cinnamon 

 on sides and rump, where the long overhairs are to a large extent 

 absent. Underparts neutral gray, overlaid by white tipped hairs; 

 anal area almost pure white. Whiskers for the most part whitish with 

 blackish-slate bases. Upper and lower lips whitish. Nose more black- 



