940 The American Naturalist. [October, 
illegitimate births, she is far behind Germany, Austria and Italy in 
point of increase of population. (Revue Scientifique, May, 1895). 
Additions to the Mammal Fauna of British Columbia.— 
MICROTUS PRINCIPALIS sp. nov. Type, ad. ¢ ; col. of S. N. Rhoads, 
No. 2346. Col. by A. C. Brooks on the Mt. Baker Range (alt. 6000 
ft.), Westminster Dist., B. Columbia, Aug. 16, 1895. 
Description: Size, largest of the western Microtine, color and pro- 
portions as in M. pennsylvanicus. Skull broad, rectangular. Incisors 
strongly produced anteriorly ; molars relatively very weak. Incisive 
foramina short and compressed, not reaching anterior molars by 3 
millimeters. 
Above, including tail and feet, grayish-brown, not darker along 
median line. Below, sooty gray, darkest where bases of hairs are ex- 
posed, distal two-thirds of hairs dull white; sides of lower neck and 
lips white. Pelage soft and silky. Fourth loop of m. 1 triangular, 
meeting fifth loop medially, the latter nearly twice as large as former 
and scroll shaped. The same remarks apply to the last two sections 
of m.2, Trefoil posterior section of m. 3 one and two-thirds length of 
anterior section of same tooth, this section being composed of an ante- 
rior loop and two opposing triangles. The formation of m.1 is as fol- 
lows: an anterior subcircular loop opening broadly into two angular 
wings whose lateral points form the anterior pair of a series of five 
angles on the inner and four on the outer sides of the tooth, including 
the opposite angles of the posterior loop and the lateral points of two 
outer and three inner closed triangles. 
Measurements: Total length 246 millimeters; tail vertebra (tip 
missing), 78-+- ; hind foot, 29.5. Skull: basilar length, 36; length of 
nasals, 11.6; interorbital constriction, 5.2; zygomatic expansion, 
23.2; crown length of molar series, 8 ; length of mandible, 25; 
greatest breadth of mandible 12.5. 
This large Vole need be compared with only one described species, 
Microtus macropus (Merriam) from the mountains of Idaho. The 
most decided differences which can be noted from Dr. Merriam’s de- 
scription and figure are in the molar dentition as particularized above 
and which can best be understood by a comparison with the diagnosis 
and plate If in North American Fauna No. 5. Besides the type, Mr. 
Brooks sent me a two-thirds grown specimen of this Vole which is very 
similar in color to type, with softer and shorter pelage. Its tail is 
unicolor, dark and very thinly haired. 
