MURIDA—ARVICOLINAS—MYODES OBENSIS. 241 
MYODES OBENSIS, Brants. 
Myodes obensis, BRANTS, Muizen, 1527, 55.—KEYSERLING and Buasius, Wirb. Europ. vi, 1840, pp. vii and 
32.—MIDDENDOREF, Sibirische Reise, ii, pt. iii, 1853, 99, pl. ii, f. 7, 8, 9, and pls. Vili, ix, x, f. 
2.—BairD, M. N. A. 1857, 559.—CouEs, Proc. Acad. Nat. Sci. Phila. 1874, 195. 
Arvicola (Georychus) helvolus, RICHARDSON, F. B.-A. i, 1829, 128. 
Georychus helvolus, AUD. & Bacu. Q. N. A. ili, 1853, 84, pl. exx, f. 1. 
Myodes helvolus, Dati, Alaska and its Resources, 1870, 577. 
Arvicola (Georychus) trimucronatus, RICHARDSON, App. Parry’s 2d Voy. 1825, 309; F. B.-A. i, 1829, 130. 
Georychus trimucronatus, AUD. & Bacu., Q. N. A. iii, 1853, 86, pl. exx, f. 2, 3. 
Myodes trimucronatus, Dau, Alaska and its Resources, 1870, 577. 
Myodes albogularis, WAGNER, Suppl. Schreber, iii, 1843, 602. 
Diacnosis.— WV. auriculatus, pollice ungue depresso obtuso ligulato instructo, 
unguibus digitorum manus 3-4" elongatis sed simplicis, pedibus modicé hir- 
sutis, vertebris caude pedibus brevioribus; note@o concolore, flavo-ferrugineo in 
capite obscuriore, gastreo dilutiore, pedibus fuscis. M. lemmo staturd formdque 
par; long. tot. 4-6 poll., capitis 14-13, mantis cum ungue longissimo 3-2, pedis 
3-3, caude nude 3—», caud@ comate 3-5. 
Has.—Americe Septentrionalis regionibus occidentali-borealibus. Asia. 
Form strictly that of the Norway lemming; ears with a perfectly-devel- 
oped conch, though small (about + high on the back, + from the notch in 
front) and buried in the fur; fore feet hairy on top, the longest hairs reach- 
ing the ends of the claws, never much when any longer; palms mostly naked, 
nearly as in ordinary Arvicola, and tuberculate; pollex obsolete, but in its 
place a very large appressed strap-shaped claw, with obtuse or truncate end, 
sometimes showing two or three minute points (“‘trimucronatus”); all the 
other claws simple (never showing the peculiar quasi-duplication of those of 
Cumculus torquatus), arched, acute, longer than in Arvicola, never so decidedly 
fossorial as in Cuniculus; third finger longest, fourth nearly as long, second 
reaching to base of third claw, fifth much shorter still; hands, including claws, 
only about $ the feet; feet above, like the hands, hairy to the ends of the 
claws, or the longest hairs slightly surpassing the claws; soles incompletely 
furry, the bases of the toes naked; second, third, and fourth toes subequal 
and longest; fifth about reaching base of fourth; second shorter still. Tail- 
vertebr shorter than foot, with the hairs equal to or rather longer than foot; 
copiously comous, the terminal pencil frequently longer than the vertebral 
portion. Pelage long, fine, soft, and mollipilose, the longer hairs quite lus- 
trous; whiskers about equaling the head, very delicate, not numerous; muffle 
completely hairy except the nasal papille. 
Entire upper parts uniform rich ruddy rust color, sometimes more 
16 M 
