MURIDA—ARVICOLIN ®—CHILOTUS. 207 
Suscenus CHILOTUS, Baird. 
Arvicola sp., AUCTORUM. 
= Chilotus, Barrp, M. N. A. 1857, 516 (type, 4. oregoni Bach.).—Covues, Proc. Acad. Nat. Sci. Phila. 1874, 190. 
Cuars.—Very small. Pelage and proportions of parts as in Myonomes, 
but the ears ‘small, orbicular, the marginal portion or helix incurved all 
round, bounding a distinct fossa innominata; the upper and lower roots so 
close together as to be confluent externally, and thus enclosing the meatus 
entirely in the anterior rim, however low. Surfaces of the ear almost naked”; 
plantar tubercles only 5 (2). Dentition combining the anterior lower molar 
as in Myonomes, with the middle and back upper molars as in Pedomys or 
Pitymys (other teeth as in Arvicola generally, and therefore not diagnostic). 
Further details of this section are given under head of its type and only 
known species. 
ARVICOLA (CHILOTUS) OREGONUS, Bachman. 
Oregon Meadow Mouse. 
Arvicola oregoni, BACHMAN, Journ. Acad. Nat. Sci. Phila. viii, 1839, 60; Townsend’s Narrative, 1839, 315.— 
Aup. & Bacu., Q. N. A. iii, 1853, 232, pl. elxvii, f. 3. 
Arvicola (Chilotus) oregoni, BArrD, M. N. A. 1857, 537. 
Arvicola (Chilotus) oregonus, Cours, Proc. Acad. Nat. Sci. Phila. 1874, 190. 
Dracnosis.—Arvicola minimus (8-34-poll.), palmis dimidium plantarum 
(4:3); cauda capite longiore (14); auriculis exiguis, occultis, subnudis, mar- 
gine plicata. Coloribus feré ut in A. ripario. 
Least Meadow Mouse, with the colors much as in A. riparius, the ears 
small, hidden, nearly naked, with folded margin and the meatus rimmed about ; 
3-34 inches long, tail 14, or with the hairs 14, thus longer than the head, and 
nearly twice as long as the soles, these twice as long as the palms. 
(No. 3233.) At first sight, this little animal looks like a half-grown 
riparius ; the next glance, however, shows that it is perfectly adult, and 
further examination reveals the peculiarities given in the foregoing diagnosis 
and in the notice of the subgenus. The fur has exactly the texture of that 
of riparius, and the coloration is much the same as in typical examples of 
the latter—a grizzle of yellowish-brown, rufous-gray, and black, darkest along 
the middle line of the back; beneath dark plumbeous, strongly hoary; tail 
indistinctly bicolor, to correspond. In fact, the external characters, both of 
color and proportions, are so much like those of riparius, with one exception, 
