RODENTIA-ARVICOLIUAE—ARVICOLA MODESTA. 
535 
Mehsurements. 
Head and body, (dried)-... 
Tail vertebras__ 
with hairs_ 
Hind feet, from heel_ 
Longest toe_......_ 
Fore foot_..._ 
Ear... 
Skull, length .. 
width...___ 
Proportions of skull. 
Inches. 
3. 50 
2.00 
2. 20 
. 90 
.27 
.45 
1.12 
.100 to 55. 
Skull .—The skull of this species has rather a short muzzle, and a long cranial portion which, 
when it is narrowed into the interorhital space, is anterior to the middle point of the skull. 
The distance from the upper molars to the posterior face of the incisors is one-third that from 
the incisors to occiput. The posterior upper molar has a supplementary internal lobe projecting 
from the inner edge of the posterior bent crescent, making five internal salient angles, and 
three external, besides the posterior rounded space. The anterior lower molar has one posterior 
triangle, three external and three internal, besides the anterior trefoil, the external lobe of 
which is thus converted into a triangle ; in this trefoil, again, the indentations between the ante¬ 
rior loop and the lateral on either side come so close to each other as very nearly to isolate the 
anterior loop from the inner lateral, and add a fourth internal triangle. There are five well 
developed salient angles internally, and five externally, the fifth formed by the anterior loop of 
the trefoil, the inner side of which almost produces a sixth internal angle. 
The specimen described above was collected by Mr. Peale on Puget’s Sound, and is the original 
of the species, as established in his report of the Mammals and Birds of the United States 
Exploring Expedition under Captain Wilkes. 
ARVICOLA MODESTA, Baird. 
Sp. Ch.— Size of A. pinetonm, or larger. Ears moderate, well furred, rather shorter than the large fore feet, (. 35 to . 40). 
Tail vertebrae scarcely longer than the head, (. 9); with the hairs, one-third the head and body. Fur long, soft, . 4 of an 
inch. 
Above, almost black, hairs with faint yellowish brown tip. Beneath, hoary plumbeous, the line of separation not very 
distinct. Tail like the corresponding regions of the body. Feet dark brown. 
Middle upper molar with five triangles, although the indentations between the two last do not quite meet. 
Although the specimen collected of this Arvicola is not quite grown, the skull shows that it 
would not attain to much greater size, and that it consequently is among the smaller of the 
American species. The whiskers are nearly as long as the head. The ears are entirely con¬ 
cealed beneath the fur, although they are quite large, .35 of an inch long, and about as broad, 
with well developed antitragus ; they are covered quite densely with long hair on both sides. 
The hind feet are somewhat mutilated, so that it is difficult to determine their exact proportions, 
hut they appear short in proportion to the fore feet. These, indeed, seem unusually long, 
measuring .4 of an inch, as far as can he made out; the longest finger, .22. The estimated 
