MURID #—ARVICOLINA—ARVICOLA RIPARIUS. 157 
Arvicola alborufescens, EMMONS, Rep. Quad. Mass. 1840, 60 (Massachusetts ; partial albino).—DEKay, N. 
Y. Zool. i, 1842, 89 (same as Emmons’s). 
Arvicola hirsutus, EMMONS, Rep. Quad. Mass. 1840, 60.—DrKay, N. Y. Fn. i, 1842, 86 (same as Emmons’s). 
Arvicola nasuta, BACHMAN, Journ. Acad. Nat. Sci. Phila. viii, pt. ii, 1842, 296 (Massachusetts),—AuD. & BAcu., 
Q. N. A. iii, 1853, 211, pl. elxiv, f. 2 (Massachusetts, New York, and Michigan).—LEConTE, 
Proc. Acad. Nat. Sci. Phila. vi, 1853, 407 (quotes ‘““Wiegmann’s Archiv, 1843, 52, and Schinz, 
251”). 
Arvicola oneida, DrKay, N. Y. Zool. i, 1842, 88, pl. xxiv, f. 1 (young; New York).—LEConrT®, Proe. Acad. 
Nat. Sci. Phila. viii, 1853, 406 (same as DeKay’s). 
Arvicola rufescens, DEKay, N. Y. Zool. i, 1842, 85, pl. xxii, f. 1 (Northern New York). 
Arvicola occidentalis, PEALE, Mamm. U. 8. Expl. Exped. 1848, 45 (Puget’s Sound).—LECon TE, Proc. Acad. 
Nat. Sei. Phila. vi, 1853, 408 (same as Peale’s).—Aup. & Bacn., Q. N. A. iii, 1854, 294 (same 
as Peale’s).—Barrp, M. N. A. 1857, 534 (Peale’s type described). 
Arvicola californica, PEALE, Mamm. U. 8. Expl. Exped. 1848, 46 (California).—LEConteE, Proce. Acad. Nat. 
Sei. Phila. vi, 1853, 408 (same as Peale’s)—Aup. & Bacu., Q. N. A. iii, 1854, 293 (same as 
Peale’s).—Bamp, M. N. A. 1857, 532 (Peale’s type). 
Arvicola montana, PEALE, Mamm. U. 8. Expl. Exped. 1848, 44 (Mount Shasta, Cal.)—Aup. & Bacn., Q. 
N. A. iii, 1854, 302 (same as Peale’s)—Barrp, M. N. A. 1857, 528 (California and ? Nebraska).— 
Newserry, P. R. R. Rep. vi, 1857, Zool. 61. 
Arvicola edax, LECONTE, Proe. Acad. Nat. Sei. Phila. vi, 1853, 405 (California).—Aup. & Bacn., Q. N. A. 
1854, iii, 270, pl. 154, f. 2 (taken from LeConte’s type, and description compiled from 
LeConte).—Barp, M. N. A. 1857, 531 (description from LeConte’s type). 
Arvicola borealis, LECONTE, Proc. Acad. Nat. Sci. Phila. vi, 1853, 407, exel. synon. (not of Richardson, &e. 
The species is based upom specimens from Rhode Island now in Mus. Smiths.). 
Arvicola trowbridgei, Barrp, M. N. A. 1857, 529, in text (name suggested from some supposed dental pecul- 
iarities of No. 384°;, Mus. Smiths., from Monterey, Cal.). 
Arvicola longirostris, Barrp, M. N. A. 1857, 580 (based on supposed cranial peculiarities of No. 3325, Mus. 
Smiths., from California) —NrEWBeERRY, P. R. R. Rep. vi, 1857, Zool. 61. 
Arvicola modesta, Barb, M. N. A. 1857, 535 (based on No. 324;, from Rocky Mountains; very young). 
Arvicola rufidorsum, Barrp, M. N. A. 1857, 526 (Holmes’ Hole, Mass.; a very red specimen). 
Arvicola breweri, Barry, M. N. A. 1857, 525 (bleached breed from Muskeget Island, Mass.). 
Sxutu.—The cranium of Arvicola riparius has not a single specifically 
diagnostic feature ; all its characters are subgeneric, shared by zanthognathus, 
and by the various geographical strains more or less deviating in external char- 
acters from ordinary 77parius of the United States. It averages, of course, 
smaller than that of zanthognathus or even of var. townsendi ; but the mini- 
mum of both of these is within the average of riparius. Our table of meas- 
urements indicates both size and shape so perfectly that these points need not 
detain us here. The skull is not satisfactorily distinguishable, dentition aside, 
from that of Pedomys; for the difference in the length of the nasal branches 
of the intermaxillaries, given by Baird, does not always hold. From Pitymys, 
it may generally be known (dentition aside) by being larger and not quite so 
wide for its length (as 0.59 to 1.00, instead of 0.62 to 1.00, as in Pitymys). 
It averages much larger than that of Chilotus oregoni. 
The dentition, likewise, offers nothing specifically diagnostic; all the 
species and varieties of the subgenus having the same pattern of the molar 
crowns. The present opportunity, however, is taken to fully describe the 
