498 BULLETIN 56, UNITED STATES NATIONAL MUSEUM. 



Color. — Adults in July: Upper parts light brown without any distinct Mack; belly bufty 

 brown; throat gray, inclosing a sharp, dusky chin stripe; a small spot over each nostril 

 whitish. 



Skull. — Small and narrow; nasals short and rounded or pointed at posterior end, never 

 notched; incisive foramina widest at posterior end; incisors heavy, molars light. 



Measurements. — Type: Total length, 470: tail, 202: hind foot, 07. Average of 6 adults:, 

 463,204,68. Skull of type: basal length, 55; nasals, IS; zygomatic breadth, 35; mastoid 

 breadth 25: alveolar length of upper molar series, 15. 



Remarks. — This form is distinguished from zibethieus by paler color, smaller size, heavier 

 incisors, unnotched nasals, and form of incisive foramina; from pallidas by darker color, 

 narrower skull, form of nasals and incisive foramina, and slightly heavier dentition. No 

 other comparisons are necessary. (Proc. Biol. Soc. Washington, XV, 1902, p. 119.) 



Genus MICROTUS Schrank (1798). 



Microtus Schrank, Fauna Boica, I, Pt. 1, 1798, p. 72. — Lataste, Le Naturaliste, II, 

 L883, p. 348.— Miller, North American Fauna, No. 12, July 23, 1896, p. 44 

 (Genera and Subgenera of Voles and Lemmings). 



Arvicola Lacepede, Mem. de PInstitut, III, 1801, p. 489. 



Dentition.— I.g; M£J = 16. 



Type. — Mus terrestris Linnaeus. 



Upper incisors without grooves; lower incisors with roots on outer 

 side of molar series; molars rootless; enamel pattern characterized 

 by approximate equality of re-entrant angles; m, usually with ."> 

 closed or nearly closed triangles; M 3 with 1,2, or 3 closed triangles; 

 tail nearly always longer than hind foot, terete; feet, fur, eyes, and 

 ears very variable ; thumb never with a well-developed ligulate nail. 

 (G. S. Miller, jr.) 



Subgenus MICK0TUS Schrank (1798). 



Microtus Schrank, Fauna Boica, i, Pt. 1, 1798, p. 72. — Miller, N. Am. Fauna, No. 12 

 July 23, 1896, p. 63 (subgenus). 



Palate normal; m 3 without closed triangles; m, normally with 

 5 closed triangles and 9 salient angles; m 3 normally with 3 closed 

 triangles and 7 or 8 salient angles; mamma 1 , S; plantar tubercles, (>; 

 soles moderately hairy; claws of hind feet longest; fur not specially 

 modified. (G. S. Miller, jr.) 



MICROTUS CALIFORNICUS (Peale). 

 CALIFORNIA MEADOW-MOUSE OR VOLE, 



Arvicola californica Peale, U. S. Expl. Exped., VIII, Mam., 1848, p. 46 (original 

 description). 



Microtus californicus Trouessart, Catal. Mam., Pt. 3, 1897, p. 563. — Elliot, Field 

 Col. Mus., Zool. Ser., II, 1901 (Synop. Mam. N. Am.).— Bailey, North Ameri- 

 can Fauna, No. 17, June 6, 1900, p. 34, fig. 3 (teeth).— Miller and Rehn, Proc. 

 Bost. Soc. Nat. Hist., XXX, No. 1, Dec. 27; 1901, p. 120 (Syst. Results Study 

 N. Am. Mam. to close of 1900). 



