Voles of the Subgenus Chilotus. 75 



Measurements. Type specimen ( 9 adult) : total length, 131 ; tail verte 

 brae, 33; hind foot, 17.5. A young adult <$ from type locality: total 

 length, 130; tail vertebrae, 32; hind foot, 17. 



Microtus serpens sp. nov. 



Type from Agassiz, British Columbia. No. 76303, tf ad., U. S. Nat. Mus., 

 Biological Survey collection. Collected December 2, 1895, by Clark P. 

 Streator. Original No. 5068. 



General characters. Similar to M. oregoni, but tail much shorter; color 

 darker; pelage much softer and longer (10 mm. or more on back in win 

 ter specimens) ; ears buried in the long fur. 



Color. Upper parts very dark brown, becoming almost dusky on pos 

 terior half of back, and everywhere profusely mixed with black-tipped 

 hairs ; under parts dark plumbeous, the belly washed with ashy or buffy ; 

 tail dusky above, pale below, and faintly edged and tipped with whitish 

 when seen from above (due to the projection of the whitish hairs of the 

 under side). 



Cranial characters. Skull similar to that of M. oregoni, but slightly 

 larger: interorbital region less 'pinched in;' interparietal tapering off 

 more gradually on each side ; teeth larger ; crowns of molar series longer. 



Measurements. Type specimen: total length, 130; tail vertebrae, 31 ; 

 hind foot, 18. Average of seven specimens from type locality : total 

 length, 130 ; tail vertebrae, 32 ; hind foot, 17.5. 



