iS94.] 191 fMiller. 
The young are uniformly grayer tlian the adults, with nose 
patclies much paler and less clearly defined, involving more or 
less the whole face, and back of the eyes shading gradually into 
the color of the body. Three of the four young have the digits 
of the hind feet white to a greater or less degree, two of them 
have the tail also tipped with white, while in one of the latter the 
digits on both of the front faet are white, and there is a narrow 
band of the same color extendiiig from chin to breast. 
Arvicola chrotorrhimis is so different from any of the known 
North American species that a detailed comparison with these is 
scarcely necessary. From Arvicola xanthognathus its very much 
smaller size and grayer color will serve at once to distinguish it. 
The prevailing tint in A. xantliognatlius is a pale wood-brown, the 
belly and feet very strongly suffused with the same color. In 
A. xa7ithognathus (seventy-three specimens) the hind foot 
averages 23.75 mm. (see Cones, Monogr. N. Am. Rodentia, p. 
201, 202, 1877). In A. chrotorrhinus the hind foot averages 19.4 
mm. Arvicola chrotorrhimis does not in the least resemble A. 
nparius except in size and general tone of coloring, its nose 
])atches, broad hind feet, peculiar skull, and pattern of enamel 
folding making it a very different animal. 
The skull of Arvicola chrotorrhinus (pi. 3, figs. 3 and 4) 
resembles in form no species of Arvicola with which I am 
acquainted. It suggests rather that of Evotomys gapjjeri (cf. pi. 
3, fig. 1). This is due to the great width and distinct concavity 
of the inter-orbital region, and the breadth and shallowness of 
the brain case, the latter peculiarity being carried even farther 
than in Evotomys gapperi. Although the resemblance to the 
skull of Evotomys is very striking in the dorsal and lateral 
aspects, it ceases entirely when the ventral surface is examined, 
since the foramen magnum is shaped as in Arvicola 7'iparius, while 
the palatal structure and broad strong tooth rows are unmistak- 
ably those of an Arvicola. On the other hand the audital bullae 
are sliphtly larger proportionally than in Arvicola riparius and 
A. xanthognathus, in this respect again approaching Evotomys. 
All the structural details of the skull are as in Arvicola, the 
likeness to Evotomys being purely superficial. 
In dentition Arvicola chrotorrhinus agrees with A. xanthog. 
nathus in lacking the posterior internal loop of the middle upper 
molar, but differs from this species and from A. riparius in the 
