MURIDA—ARVICOLINA—ARVICOLA. Lis 
B.—Cunrotus. Back upper molar with 1 external triangle and a posterior 
trefoil. Middle upper molar with 1 internal triangle. Front lower 
molar with 3 internal and 2 or 3 external triangles. Ear with a rim in 
front of the meatus, owing to meeting there of the anterior and poste- 
rior roots of the auricle. Sole 5-tuberculate(?). Fore claws not larger 
than hinder ones. Tail about 4 the head and body. Pelage ordinary. 
Of minimum size. 
C.—Prvomys. Back upper molar with 1 external triangle and a_ posterior 
trefoil. Middle upper molar with 1 internal triangle. Front lower 
molar with 2 internal and 1 external triangle. Ear unrimmed. Sole 
5-tuberculate. Fore claws not larger than hinder ones. Tail about 4 
the head and body, or a little less. Pelage ordinary. Of medium size. 
D.—Pirymys. Back upper molar with 1 external triangle and a posterior 
trefoil. Middle upper molar with 1 internal triangle. Front lower 
molar with 2 internal-and 1 external triangle. Ear unrimmed. Sole 
5-tuberculate. Fore claws larger than hind ones. Tail about 4 the 
head and body, or less. Pelage dense, mole-like. Of small size. 
Suspgenus MYONOMES, Rafinesque. 
< Arvicola of American writers. “4 
= Arvicola A, Hemiotomys, Batrp, M. N. A. 1857, 515 (type, Arvicola riparius Ord). Not of Srtys-LONG- 
CHAMPS, whose type is the European Arvicola amphibius. 
= Mynomes,* RariNesQquE, Am. Monthly Mag. ii, 1817, 45 (type, Mynomes pratensis RAFINESQUE, which 
is based on Wilson’s Meadow-Mouse, Am. Orn. vi, pl. 50, f. 3, and is therefore = Arvicola 
pennsylvanica Ord and auct.). 
= Myonomes, Cours, Proc. Acad. Nat. Sci. Phila. 1874, 189. 
Cuars.—Posterior superior molar with an anterior loop, an internal 
closed triangle, éwo external closed triangles, and a posterior crescent. Ante- 
rior inferior molar with a posterior loop, an anterior trefoil, three lateral inter- 
nal closed triangles, and two (or threet) lateral external closed triangles. 
Middle superior molar with a supplementary postero-internal triangle. (Other 
dental and cranial characters as in Arvicola at large.) Ears about equaling 
the fur, rounded, hirsute, with well-developed valvular antitragus; no pecul- 
iar construction of the concha. Tail exceeding the head in length (about 
one-third as long as head and body), fairly hirsute and with terminal pencil, 
*The original orthography is Mynomes. I do not know what, if any, meaning attaches to thig 
word, but suppose it to be compounded with pve, so that it should be spelled Myonomes, if not further 
altered into Myonomus. 
+ When there are three, the third results from change of the outer leaflet of the anterior trefoil 
into a triangle. 
