RODENTIA ARVICOLINAE ARVICOLA GAPPERI. 519 



taken from an average winter specimen. There is usually a tendency in the rufous of the back 

 to run down more or less on the sides just anterior to the hind legs. There is frequently, also, 

 a yellowish brown spot in the insertion of the whiskers, sometimes a dusky one instead. A 

 midsummer specimen (864) is of a more vivid rufous, this color tinging the sides of body and 

 head, (but not of the shoulder.) There is a bright fulvous yellow spot on each side the muzzle. 

 Two specimens of Arvicola, borrowed from the cabinet of Professor Agassiz, and labelled 

 " Lake Superior," exhibit a close resemblance to the A. gapperi, and, in fact, are scarcely to 

 be distinguished but by the rather larger size and a few other peculiarities. It is possible that 

 they may be from Massachusetts, and labelled by mistake. Were this the case with the present 

 materials only, I would have little hesitation in considering them the same ; but if really from 

 Lake Superior, (the north shore,) the remoteness of the two localities, and the difference in 

 their zoological characters, might go far to give a specific value to the otherwise trifling 

 distinctions. 



The size is rather less than that of the common Arvlcolae of the eastern States ; the head nar 

 row and rather acute. The ears are large, longer than broad, projecting beyond the fur, and 

 always visible. They are coated with short close hairs on both sides. Antitragus large. 



The hind feet are quite large and broad ; the sole hairy for nearly half its length from the 

 heel, and involving the first tubercle. The tail is quite thick, tapering but little to the tip, 

 which is terminated by a pencil of hairs, and otherwise well covered ; it is considerably longer 

 than the head, and more than one-third as long as the head and body. 



The upper parts, from the crown to the rump, are a bright and uniform rufous brown or 

 chestnut, mixed with, but not obscured by, black hairs ; the fur is generally soft and glossy. 

 The entire sides of the head and body are a dirty brownish yellow, obscurely mixed with black 

 hairs. The whole head anterior to the eyes is similar, with rather more black hairs. The 

 color of the sides is well defined against that of the back ; beneath it passes not very sensibly 

 into the yellowish white of the belly and under parts. The feet are grayish white. The tail 

 above is light brown, becoming darker near and at the tip ; beneath it is like the belly ; the 

 line of separation very distinct. 



The female is similar, but smaller, with a more slender tail . 



The specimens are very similar to those received from Mr. Jenks, except that the male has 

 considerably stouter feet and tail. The belly is rather yellower. The size generally is larger. 

 The nose appears to be longer. 



"Wo 2 - ^ 3 Lake Superior. The skull of this animal is rather long in proportion to its width, 

 but at the same time considerably depressed. There is a decided indentation or shallow con 

 cavity in the forehead just anterior to the parietal bones. The nasal bones and nasal branches 

 of intermaxillary are of equal length, and do not extend back as far as the orbit, reaching, in 

 fact, but little posterior to the anterior base of the zygomatic arch. The contracted interorbital 

 portion of the frontal bones is quite broad, as wide as is the muzzle, (.15 of an inch,) and 

 exhibits a small hole or foramen in the bone on either edge, situated at the beginning of the 

 contraction, and a little anterior to the middle of the longitudinal axis of the skull. 



The interparietal bone is somewhat lozenge-shaped, broadly obtuse anteriorly, more rounded 

 behind, on either side extending outwards in an acute angle. The line connecting the extreme 

 lateral points of the bone would cross about or a little behind its centre. The occipital foramen 

 is nearly round. The distance from the line of upper molars to the posterior base of the incisors 



