94 The Mammals of Colorado 
Key of the Species 
A. Mammae 8; plantar tubercles 6; 3d upper molar with 3 closed 
triangles; ist lower molar with 5 closed triangles. 
(Subgenus Microtus.) 
a. Larger, total length over 6.25. 
a'. Color above darker; tail short, about 25% of total length. 
M. penn. modestus, p. 95. 
b'. Color above grizzled grayish brown, sides grayish, tail 
longer, about 36% total length. M. mordax, p. 99. 
b. Smaller, total length usually under 6. Color above grizzled 
grayish brown; tail short, about 25% total length. 
M. nanus, p. 98. 
B. Mammae 8; plantar tubercles 5; 3d upper molar with 2 closed 
triangles and narrow posterior loop; ist lower molar 
with 5 closed triangles. (Subgenus Lagurus.) 
a. Size small, tail very short, less than ^ total length. 
M. pauperrimus, p. 100. 
FIG, 32. SAGUACHE VOLE, Microtus p. modestiis 
Skull showing dentition x 3 
C. Mammae 6; plantar tubercles 5; 3d upper molar with only 
2 closed triangles; ist lower molar with 3 closed triangles. 
(Subgenus Pedomys.) M. haydeni, p. loi. 
Many of the meadew voles resemble one another so very 
