MICROTUS. 199 



angles; first lower molar with five pair of reentrant angles meeting 

 behind anterior loop. 



Color. Above chestnut, hairs tipped with dusky; under parts 

 paler. Tail similar to the back, unicolor. Feet brownish. 



Measurements. Total length, 120; tail vertebrae, 22; hind foot, 

 i5. Skull: basal length, 22.3; nasals, 7; zygomatic breadth, 15.2; 

 mastoid. 12.3; alveolar length of niolar series, 6. 



298. nemoralU. {.Uicrotus), Bailey, Proc. Biol. Soc. Wash., 1898, 

 p. 8g. 



Type locality. Stilwell, Boston Mountains, Indian Territory. 



Geogr. Distr. Indian Territory and Arkansas to Council Bluffs, 

 Iowa. 



Genl. Char. Size large; ears large; third upper molar with 

 three tightly closed triangles and an irregular posterior loop; first 

 lower molar with opposite reentrant angles meeting behind the an- 

 terior loop. 



Color. Above dull chestnut lined with black on back and rump; 

 sides paler, beneath cinnamon rufous; under fur plumbeous. Tail, 

 like back above, and like belly beneath. Feet pale buff. 



Measurements. Average total length, 135; tail vertebrs, 25; hind 

 foot, 18. 1. Skull: basal length, 25.3; nasals, 7.7; zygomatic breadth, 

 16.5; mastoid, 13.4. 



E. Ohilotus. 

 Palate normal; lower third molar normally without closed tri- 

 angles; lower first molar w^ith five closed triangles and nine or ten 

 salient angles; upper third molar with two or three closed triangles 

 and si.x salient angles. Mamm;E eight, four pectoral, four inguinal. 

 Plants tubercles, five; soles hairj'. 



Fig. 42. MicROTus (Chilotos) oregoni. 



No. 289 Field Columbian Museum Coll. Nat. size. 



Lower tooth row. 

 Enlarged 5 limes. 



Upper tooth row. 

 Enlarged 5 times. 



