165. Tail not over one and one -half times as long as the hind foot; skull flat 



and wide 166. 



Tail more than one and one-half times as long as the hind foot; skull 

 high and narrow (A difficult group, with many intergrading species 

 and subspecies. A few common ones are given here.) Meadow Mice 

 or Voles 169. 



166. With eight mammae; western states 



Lagurus curtatus (Cope) Short-tailed Meadow Mouse 

 (LemmisciiS curtatus (Cope) ) 



(Several subspecies, including pallidas (Merriam), pauper^ 

 rimus (Cooper) and intermedius (Taylor) ) 

 With four mammae or nipples, all between the hind legs 167. 



167. West of the Mississippi River from Okla. to Iowa 



Pitymys nemoralis (Bailey) Western Pine Mouse 

 (Considered to he a subspecies of P. pinetorum) 

 East of the Mississippi 168. 



168. From Mass. to Ga.; upper parts chestnut; feet grayish 



Pitymys pinetorum (Le Conte) Eastern Pine Mouse 

 In Florida; upper parts paler; feet pinkish 



Pitymys parvulus Howell Florida Pine Mouse 



169. With five plantar tubercles (raised pads on sole of hind foot) 170. 

 With six plantar tubercles 173. 



170. Mammae (nipples) eight; Pacific states 



Microtus oregoni (Bachman) Oregon Vole 



(Includes M. bairdi Merriam and M. serpens Merriam) 

 With four or six mammae 171. 



171. In Louisiana 



Microtus ludovicianus Bailey Louisiana Meadow Mouse 

 In the plains states 172. 



172. Total length of adult about five inches; N. D. and Minn. 



Microtus minor (Merriam) Least Upland Vole 

 (Pedomys minor (Merriam) ) 

 Total length of adult about six to seven inches; most of the plains states 

 Microtus ochrogaster (Wagner) Prairie Vole 

 (Includes M. haydenii (Baird) ) 



173. Middle upper molar with four closed triangles and a posterior loop; 



widely distributed, westward to the Rockies and into Washington 

 Microtus pennsylvanicus (Ord) Common Meadow Mouse, 

 Vole 

 Middle upper molar without a fifth loop or triangle 174. 



174. With two pairs of mammae, one between the front legs, the other be- 



tween the hind legs; Ariz, to Texas 



Microtus mexicanus (Saussure) Mexican Vole 

 With four pairs of mammae 175. 



175. Snout yellowish; usually also yellowish around the ears and the rump; 



eastern states 



522 



