Vol. 30, pp. 29-30 February 21, 1917 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



A NEW SUBSPECIES OF MEADOW MOUSE FROM 



WYOMING. 



BY VERNON BAILEY. 



The common valley meadow mouse of southwestern Wyoming 

 is so strikingly different from typical Microtus montanus, to 

 which it is most nearly related, that it seems necessary to rec- 

 ognize by name this extreme variant which gradually changes 

 in characters across Nevada and Utah, and reaches its maximum 

 variation in Wyoming. It occupies the meadows along streams 

 in the arid sage-brush country of the Bear River, Green River, 

 and Wind River valleys, and has the general habits of the larger 

 darker M. montanus farther west. 



Microtus montanus caryi subsp. nov. 



Type from Milford, Fremont County, Wyoming; adult (?, No. 168,670, 

 U. S. National Museum, Biological Survey Collection. Collected by 

 Merritt Cary, May 8, 1910; original number 1912. 



General characters. — About the size of montanus, but with relatively 

 shorter tail and paler coloration throughout. 



Color. — In spring pelage before the summer moult, upper parts warm 

 Imffy gray with a rather coarsely grizzled effect of buff and black tipped 

 hairs; top of tail dusky; sides of nose clear buff; lower parts, feet, and 

 lower surface and sides of tail white or silvery gray. Late summer pelage 

 after the fall moult not shown in the collection, but probably darker. 

 Young duller and more brownish with darker feet, tails, and under parts. 



Skull. — Very similar in size and form to that of typical montanus, but- 

 less heavily ridged in old males and with less sloping supraoccipital. 



Measurements. — Type: Total length, 177; tail, 45; hind foot, 21 ; of an 

 adult female topotype, 148, 41, 20. 



Skull of type. — Basal length, 27.5; nasals, 7; zygomatic breadth, 16; 

 mastoid breadth, 13; alveolar length of upper molar series, 7. 



10— Proc. Biol. Soc. Wash., Vol. 30, 1917. (:>9) 



