MURID#—ARVICOLINA—PEDOMYS. 209 
TaBLe LIT.—Measurements of three specimens of ARVICOLA (CHILOTUS) OREGONUS. 
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2 Nose to-- Tail to— 
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5 ehh ies Heel) Ae ese | Ee eee feral a 
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a || Aa | Blalolalela | a\a|8 
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4323 | ¢ | Dry...| Aug.—, 1855} Shoalwater Bay ...... -. J. G. Cooper..-.-..-.|-- alias A eee 3, 50/1. 101. 25 0. 33.0. 66,0. 28) 
2529 Ale...) —— —,1855| Steilacoom ............. G. Suckley ...-.-.-..|0. 43.0. 2: 5/1. 00)3. seal 20/1. 35.0. 35.0, 61 0. 33) 
| ee | 
2533 |. --do ...| —— —,1855/ Tomales Bay..........-. E. Samuels. .....--..|0. 400. 80 1. 05)3, 75:1. 00)1. 15,0. 30.0. 56 0. 30 
28370 $-GO)<=2| sn asevionuc ance Puget Sound ? a ee alae 255 \ldo- | Sas] oma} oe ees 
CAEch | a Prope ere lee a ae eee eS ets ces pio b Worl aaa en 
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Nore.—Nos. 8370-71, apparently of this species, are too young for positive identification. The teeth are scarcely cut; 
but, so far as we can judge, the back upper molar will have but one external closed triangle, and a posterior Y-shaped trefile. 
The meatus seems to be surrounded by a faint rim, but the upper margin of the ear is not inflected, the concha being per- 
tectly flat. 
Suscenus PEDOMYS, Baird. 
Arvicola sp., AUCTORUM. 
= Pedomys, BarrpD, M. N. A. 1857, 517 (type, Arvicola austerus LeC.).—Cours, Proc. Acad. Nat. Sci. 
Phila. 1874, 190. 
Cuars.—Postero-superior molar with an anterior transverse loop, two 
interior triangles, one exterior triangle, and a posterior U-, V- 
loop (as in Pitymys and Chilotus). 
, or Y-shaped 
Medio-superior molar with an anterior, 
two exterior, and only one interior triangle (lacking the supplementary postero- 
interior spur or triangle of MZyonomes). Antero-inferior molar with a posterior 
transverse loop, two interior closed triangles, one exterior closed triangle, 
another exterior and another interior open triangle, and an anterior irregular 
trefoil. Ears 
inflected margin of conch or rim in front of meatus; antitragus highly val- 
Other molars as in <Arvicola at large. without 
concealed, 
vular, as usual. Tail in the type of the subgenus about equal to the head 
(about one-third the head and body), in other species not more than one- 
fourth the trunk, and thus as short as in Pitymys. Perfect plantar tubercles 
only five. 
Seay shorter oe 
rather ‘ 
Under head of Arvicola we have already diagnosticated this section, and 
No special cranial characters, and external form as in Myonomes 
“austere” 
or much as in Arvicola at large. 
after the further remarks just made there is little to say. 
Pelage grizzly and 
; the under parts usually with a peculiar muddy tinge. 
There are no tan- 
gible cranial characters; and, as to the external characters, they are with difti- 
culty describable as any different from those of Myonomes; but the tail is 
shorter, and the animals appear to be even more squat and bunchy than J/. 
riparius. There are only five perfect plantar tubercles, though the rudiment 
14M 
