1922] KcUogg: Synopsis of Microtus Mordax 293 



Microtus mordax angusticeps Bailey 



Northwest Coast Meadow Mouse 



Microtus angusticeps Bailey (1898, p. 86). 



Microtus angusticeps, Bailey (1900, p. 51). 



Microtus angusticeps, Elliot (1903, p. 177). Eequa, Del Norte County. 



Microtus toionsendi, Elliot (1907, pp. 295-296). Eureka, Humboldt 



County. 

 Microtus mordax angusticeps, Grinnell (1913, p. 320). 



17087 

 Type specimen. — Male adult; no. , Biol. Surv. coll., U. S. 



Nat. Mus. ; Crescent City, Del Norte County, California ; June 16, 

 1889; collected by Theodore S. Palmer; original no. 151. 



Range. — Northern humid coast region of California from Mendo- 

 cino, Mendocino County, north to Crescent City, Del Norte County. 

 Vertical range, so far as known, not over 100 feet above sea level; 

 zonal range Transition. (See map, fig. CC.) 



Total number of specimens examined, 44, from the following 

 localities in California. Mendocino County : Fort Bragg, 16 ; Mendo- 

 cino, 1. Humboldt County: Trinidad, 3; three miles west of Areata, 

 16 ; Eureka, 4. Del Norte County : Crescent City, 4. 



Diagnosis. — Size medium (hind foot, 20 to 23 mm. ; condylobasal 

 length of skull in largest individuals, 28.4 mm.). Skull normally 

 small, narrow and lightly built (ratio of zygomatic breadth to con- 

 dylobasal leng-th about 55 per cent), and not conspicuously ridged in 

 adults ; auditory bullae small and flattened below meatus ; pelage in 

 mass effect approaching russet; ears relativel}^ large (14 to 15 mm.). 



Measurements. — Average of 10 specimens : Total length, 174.3 mm. 

 (162-194) ; tail vertebrae, 61.2 mm. (56-74) ; hind foot, 22.0 mm. 

 (21-23) ; condj'lobasal length, 26.59 mm. (25-28.4) ; occipito-nasal 

 length, 26.6 mm. (25.5-28.2) ; basilar length, Hensel, 23.32 mm. (22- 

 24.9) ; nasal length, 7.77 mm. (7.2-8.6) ; zygomatic width, 14.89 mm. 

 (14.1-15.7) ; interorbital constriction, 3.71 mm. (3.5-4) ; interparietal 

 width, 8.43 mm. (8.1-8.9) ; shelf of bony palate, 13.06 mm. (12.4-13.9) ; 

 height cranium at bullae, 9.92 mm. (9.5-10.4) ; mastoid width, 11.88 

 mm. (11.3-12.5) ; length upper molar series, 6.5 mm. (6.1-7) ; length 

 mandible, 15.98 mm. (15.2-16.8). 



Color. — Upperparts and sides as a rule brighter than in any other 

 race of the mordax group in California. Dorsal area not so strongly 

 darkened by presence of long overhairs. In fresh pelage: ground 

 color of upperparts varying from argus brown to auburn. Light 

 terminal portions of hairs grading from ochraceous buif to warm buff; 

 basal portions of hairs blackish plumbeous. Long overhairs ranging 

 in shade from mars brown to seal brown. Color of upperparts changes 

 rather abruptly to lighter color of sides. The light or warm buff hairs 

 of sides are more conspicuous because of absence of long overhairs, 

 and sides are not grayish in mass effect. Underparts with pale 



