Drummond Vole 519 



species an additional posterior inner loop; m'^ with 3 closed 

 triangles (except in chrotorrhinus and ahhreviatus groups)." 



Third, of the species pennsylvanicus,'' of which drummondi , 

 and most likely all shown on the map, are local forms. 



"MiCROTUS PENNSYLVANICUS. — Size, medium; tail, at oen- 

 least twice as long as hind-foot; fur, long, overlaid with coarse char- 

 hairs; ears, moderate, conspicuous above fur in summer, al- ^^"^^^ 

 most concealed in winter pelage; colours, dusky gray or 

 brownish; skull, long, well arched, and rather smooth; middle, 

 upper molar, with four triangles and a posterior loop. 



'''Summer pelage'. Upper parts, dull chestnut brown, vary- colour 

 ing to bright yellowish chestnut, darkened along the back with 

 coarse black hairs; belly, dusky gray or tinged with cinnamon; 

 feet, brownish; tail, dusky above, slightly paler below. 

 Winter pelage: Duller and grayer throughout; tail, indis- 

 tinctly bi-colour. Young: Blackish. 



"Skull, long, usually not angular or much ridged; incisors, cranial 

 projecting well in front of nasals; incisive foramina, long, acters 

 occupying two-thirds of the space between the molars and 

 incisors; bullae, moderately large and 



well rounded; molar series, long; m2 | (im;W|^K^^U^ 

 with 4 closed triangles and a posterior inside J 



loop; m3 with an anterior crescent, 3 | ^5ftMA^^'^!A9 

 closed triangles, and a posterior loop fig. Mp-Moiar enamei pattern of 



.1 . ■, ■, '111 Microtus pennsylvanicus (xs) 



with two mner lobes; mi with *: closed From BaUey. Fauna .7, Biologkal Suney. 



. ' ., "^ , U. S. Dept. Aijr. 



triangles, anterior treioil, 4 outer and 



5 inner salient angles; mi^ with 3 long inner and 3 short salient 



angles. 



Average of 5 adults from Washington, D. C. : Total length, meas- 

 171 (6| inches); tail vertebrae, 46 (lit inches); hind-foot, 21.2 ments 

 (H inches); skull (No. 30321, '^ ad., from Washington, D. C), 

 basal length, 27.4 (lA inches); nasals, 8.3 (H inches); 

 zygomatic breadth, 17.2 {\\ inches); mastoid breadth, 12.7 

 (I inch); alveolar length of upper molars series, 7.2 (A inch). 



To this Bailey adds for drummondi:^ 



''Ibid., p, 17, ^ Ibid., pp. 22-23. 



