522 U. 8. Pp. R. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
ARVICOLA RIPARIA, Ord. 
Meadow Mouse. 
Arvicola riparius, Onp, J. A. N.Sc., Phila. IV, 1, 1825, 305. 
Aup. & Bacu. N. Am. Quad. IIT, 1854, 302. 
Arvicola palustris, Haru. F. Am. 1825, 136. 
Arvicola pennsylvanica, (ORD,) Aup. & Bacu. N. Am. Quad. I, 1849, 341; pl. xiv. 
?? Arvicola riparius. Kennicott, Agri. Rep. U. S. Patent Office for 1856, (1857,) 1045. pl. xiii. (Zongipilis.) 
Sp. Cu.—Size large. Head and body measuring 43 inches. Tail more than one-third this length. Feet very large, 
scaly. Hair rather short. Above, dark brown, varied with reddish or yellowish brown ; beneath, pure ashy plumbeous ; 
tail and feet dusky, the former scarcely lighter beneath. : 
As Ihave not yet satisfied myself of the precise limits within which this animal may vary, 
and how far the numerous species described by authors are worthy of retention, I have coneluded 
to give a minutely detailed description from a specimen so near in locality and appearance to 
the original A. riparia as to serve as a suitable standard of comparison. I have accordingly 
selected a fresh specimen caught at Carlisle, Pennsylvania, in September, and agreeing exactly 
with one from Philadelphia, presented by Major Leconte as the type of 4. riparia, 
Fresh specimen from Carlisle, Pennsylvanta.—Body broad and stout. Head considerably 
pointed ; the muzzle projecting .15 beyond the upper incisors. The upper Hp is bifid to near 
the nose, to which there extends a shallow naked groove, continued across the nose, sepa- 
rating the two nostrils, which are slightly swollen around their aperture. The extreme tip 
of the nose is thus naked, the hair, however, so far forward that this naked tip eannot be 
seen when viewed from above. The eye is small, about .15 an inch in longitudinal axis; its 
centre midway between the nose and the ear. The ears are almost orbicular, nearly as broad 
as long; the antitragus much developed, almost semicircular; the chord of its are .2 long 5 
its surfaces are thinly covered with long hairs, which project beyond the margin, but do not 
obscure it. 
The thumb of the fore foot is obsolete, the corresponding claw springing directly from the 
skin; this is well shaped, and similar to the others, but not so large and blunt at the point. 
The third and fourth fingers are about equal; the second claw reaches the end of the third 
finger; the fifth claw reaches the end of the second finger. The sole of the hind foot is 
sparsely hairy from the heel to the tubercles. The central three toes are longest ; the fourth 
longest of all ; the first and fifth are inserted on shorter metatarsals than the central ones ; the 
claw of the first extends to the cleft between the second and third; the fifth toe (exclusive of 
claw) reaches the cleft between the third and fourth. 
The tail is about four-ninths the length of head and body ; it is subquadrangular, tapering, 
and sparsely covered with stiff hairs, which do not conceal the annuli; there is a scanty peneil 
of hairs at tip. 
Teats, four inguinal, and four pectoral. 
The prevailing color of the back and sides is a reddish brown, the shade of reddish dis- 
tinctly appreciable, the hairs being broadly marked subterminally with this color. They are 
tipped with black, which, with the intermixture of black hairs, causes a strong shade of dusky, 
uniformly diffused. The lower parts of the sides are rather purer yellowish brown; the belly 
whitish ashy, tinged with plumbeous, and the faintest possible shade of brown. The feet and 
tail are dusky, the latter scarcely paler beneath. 
