178 MICROTINii: 



Genus : 3. MYOPUS Miller. J| 



1844. Myodes Lilljeborg, Ofversigt af Kongl. Vetenskaps-Akad. * 



Forhandl. Stockholm, 1, p. 33 (in part). 

 1910. Lemmus Trouessart, Faune Mamm. d'Europe, p. 199 (in part). 

 1910. Myopus Miller, Smithsonian Miscell. Coll., 52, p. 497. 



Genotype. — Myodes schisti color Lilljeborg. 



Range.- — Southern Norway and Sweden eastwards across 

 Russia and Siberia to the Sea of Okhotsk. Apparently strictly 

 confined to the fir forests of northern Europe and Asia. ] 



Characters.- — External form vole-like, but a little more thick- 

 set than in Synaptomys. Fur soft and dense; colour slaty 

 black with a more or less intense, extensive, and well-defined 

 rufous mantle. Ears small but well developed, rounded, pro- 

 vided with a meatal valve (" antitragus "), and well haired within 

 and without; projecting very little beyond the fur. Hands and 

 feet slender, nearly as in normal voles ; the fore-claws not en- j 

 larged but shorter and more slender than those of the hind-foot ; 

 the palms and soles with well-developed pads and not exception- ; 

 ally hairy. In the hand the thumb is small and is furnished with j 

 a large flattened nail, resembling though smaller than the thumb- j 

 nail of Lemmus; the two longest digits (III and IV) are sub- \ 

 equal and have long metacarpals which slightly exceed the \ 

 phalanges taken together in length ; digits II and V are con- 

 siderably shorter and subequal; the ungual phalanges of all 

 the fingers are small and normal, much shorter than the com- j 

 bined lengths of the first and second phalanges. Palms naked, | 

 save for a few scattered and minute hairs, granulo-tuberculate, j 

 with four well-developed pads (that normally present at the 

 base of the thumb being absent), of which the postero-external 

 is larger and more elongate than usual. Hind-foot with normal 

 claws and digits; soles densely haired behind the pads, naked 

 and like the palms in front; plantar pads six, the four anterior 

 at the bases of the digits large and somewhat crowded, the two 

 posterior small and rounded. Tail short, slightly longer than 

 the hind-foot, rather densely clothed but the annulations not 

 quite concealed ; terminal pencil slender and about half the 

 length of the vertebral portion or tail proper. Mammae, 2 — 2 = 8. 



Skull in all essential respects similar to or approaching that 

 of Lemmus. It is distinguished by its smaller size and lighter 

 build; the zygomatic arches are a little less widely expanded, 

 but the jugals are somewhat more reduced ; the braincase is a , 

 little narrower, the squamosals more widely separated anteriorly, 

 and the posterior or intertemporal breadth of the frontals is 

 much greater; the supratympanic fenestra of each squamosal 

 is very small, smaller than in Lemmus. The rostrum is shorter 

 than in Lemmus, but more slender than in Synaplomys, the 

 anterior palatal foramina being large as in the latter genus. 

 The cheek-teeth are relatively heavy, the length of a tooth-row 



