The American Voles of the Genus Evotomys. 1^1 



Evotomys dawsoni ■Merriain. 



Ei'otomijs dawsoni Merriam, American Naturalist, XXII. 649, Jul\', 1888. 



Ti/pelocdlHi/. — Finlaj'son River (a iiorthern source of Liard River, NWT., 

 lat. 61° 30' N., long. 129° 30' W., altitude 3000 feet [915 meters |). 



Geographic di.slribution. — From Finlayson River and Fort Liard west to 

 Yakutat and .luneau, and north along the coast to Prince William Sound. 



General characters. — Robust, with large body and shoi't tail ; tail rareh' 

 twice as long as hind foot, well haired, but not bristly as in ratlins ; ears 

 prominent and well haired ; colors bright. 



Color. — Dorsal stripe sharply defined, reaching from just back of eyes 

 to base of tail, bright ferruginous with few dark hairs; sides, face, and 

 rump bufty-ochraceous ; belly thinly washed witli })ale l)uff; tail dis. 

 tinctlv bicolor, clear bufiy-ocliraceous below, a mixture of rufous and 

 blackish hairs above; feet thinly clothed with buff y and dusky hairs; 

 ears covered on inner surface of projecting tips with short, rufous hairs ; 

 an indistinct yellowish postauricular spot ; eyes encircled by faint yel- 

 lowish rings ; tufts of rufous hairs fall back from in front and till openings 

 of ears; a small white throat patch marks 10 out of 29 specimens ; spot 

 covering side glands inconspicuous. 



Cra)il((l cJiaracters. — Skull large and thick-walled, relatively short, wide, 

 and angular, with the smallest and flattest audital bullae of any Ameri- 

 can species; nasals terminating on a line with ascending arm of pre- 

 maxilhe, pointed in immature, rounded in adult skulls, never truncate; 

 pterygoids strong and prominent, the ends siiowing in lateral profile 

 above the small, flattened bullae ; basioccipital unusually wide between 

 bullie; i)alatines short, rectangular, with lateral bridges incomplete ex- 

 cei)t in skulls of old individuals ; posterior margin of palate with a central 

 notch, deepest in immature specimens ; incisors large, with dark orange 

 enamel ; molar series long and narrow. 



Measareini'iits. — Average of 8 adults from Yakutat (4 ^ and 4 ? ) : total 

 length, 144; tail vertebrie, 33; hind foot, 20. Skull, No. 73560, adult J^, 

 basal length, 22.5; nasals, 7.5; zygomatic breadth, 14 ; mastoid breadth, 

 12.2 ; alveolar length of upper molar series, 5. 



Reiuarl-s. — The type was collected June 23, 1887, by Dr. George M. 

 Dawson, Director of the Geological and Natural History Survey of 

 Canada. Through the kindness of Dr. Dawson it is now before me for 

 comparison with a large series of skins and skulls from Yakutat and 

 Juneau, Alaska. It is gratifying to find that the type agrees in every par- 

 ticular with this series of specimens, and that the name Ecotomys dairsoni 

 stands for this large and handsome species. The type was not fully 

 adult, and unfortunately was mounted from a half relaxed skin, so that 

 the size is greatly reduced. The tail vertel)r;e were not removed, and the 

 tail has dried short, but the hind foot and ear give reliable measuiements 

 for comparison. The skull is badly broken, but the teeth give good 

 characters for comparison. The openly communicating loops and the 

 length of the molar series as a whole maybe perfectly matched in slightly 

 immature skulls from Yakutat. 



28— Biol. Soc. Wash., Vol. XI, 1897 



