MURID.E— ARVICOLIISLE— EVOTOMYS RUTILUS. 137 



hair ; and, in some specimens, especially in winter, the entire sole is covered 

 with fur, although no hairs really grow on the tubercles. The 2d, 3d, and 

 4th toes are about equal in length, and longest; the 5th is only about half 

 their length; the 1st still shorter; all bear ordinarily developed nails. On 

 the whole, the furring of the feet of this animal is much heavier than that of 

 Arvkolce. living in less rigorous climates, and is only surpassed in length and 

 density by that of the Lemmings. The tail is similarly indicative of a hyper- 

 borean habitat, and merits special attention, since the difference in this mem- 

 ber between true rutilus and its conspecies of lower latitudes is the most 

 conspicuous feature. If we call to mind the stumpy, heavily-furred, almost 

 rabbit-like tail of a Lemming, and then lengthen it to half-way between this 

 and the tail of more southern Arvicolce generally, we shall have about hit the 

 mark. Even including the unusually long pencil of hairs at the tip, the tail 

 is barely or not twice as long as the sole, and it often falls much short of this 

 proportion. It is remarkably thick, and hardly diminishes in caliber to the 

 very tip, which is obtuse. It is densely hairy throughout, having no trace of 

 scales or annuli ; and the long, thick, terminal pencil averages fully a third of 

 the length of the vertebral portion. 



The size and relative proportions of this animal are sufficiently illustrated 

 in the table below to render further notice here unnecessary. 



The peculiar color of this, the type of the genus — and the shade is 

 shared to a greater or less extent by all the forms of the genus with which we 

 are acquainted — is almost of itself diagnostic. The middle lengthwise area 

 of the upper parts, from the forehead, or even the snout, to the tail, are of a 

 bright rusty-redjiOr brick-color, just as if a trace of orange, or even a touch 

 of vermilion, were mixed with the rufous-brown that marks so many other 

 Arvicolines. This rusty-red always has a few black longer hairs in it: some- 

 times these are so sparse that its uniformity is not perceptibly removed, but 

 at others the very central dorsal line becomes a little blackish, especially over 

 the haunches. The width of this dorsal area and its sharpness of distinction 

 are very* variable; sometimes the red is spread over the whole back, and 

 washes imperceptibly into the color of the sides, and at other times it is 

 narrow and pretty distinct. The color of the sides is luteous, like unbaked 

 yellow clay, but is often grayish-yellow rather than yellowish-gray. Just as 

 the back fades into the sides, so these wash out into the color of the belly, 

 without much sharpness of definition, though the line of change is usually 



