RODENTIA ARVICOLINAE ARVICOLA MODESTA. 535 



Measurements. 



Skull. The skull of this species has rather a short muzzle, and a long cranial portion which, 

 when it is narrowed into the interorbital 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. Pealeon 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. Cn. Size of A. pinet&rum, or larger. Ears moderate, well furred, rather shorter than the large fore feet, (. 35 to . 40). 

 Tail vertebra 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, 

 but they appear short in proportion to the fore feet. These, indeed, seem unusually long, 

 measuring .4 of an inch, as far as can be made out; the longest finger, .22. The estimated 



