13t 
ate nearly plane; nasals projecting anteriorly. Animals of lithe and 
supple form, quick in movement, with large, bright eyes, pointed, mobile 
snout, prominent ears; and lengthened limbs and tail. Abundant in 
temperate and warm climates, not reaching the Arctic Seas. Found 
throughout South, Central, and most parts of North America. 
Arvicoline.—Molars normally rootless (except in Hvotemys), prismatic, 
with flat crown and serrate periphery. Incisors often broader than high, 
root of under incisor causing a protuberance, if any, on the inner side of 
the mandible, at or near notch between condylar and descending process ; 
descending process of siandible hamular, the apex of the hook attaining 
the level of the molars; palate highly arched; nasals not projecting be- 
yond pre-maxillaries. Animals with squat and heavy shape, slow move- 
ment, small eyes, blunt snout, inconspicuous ears, and shortened limbs 
and tail as compared with Murine. Not known to occur further south 
than Mexico; most numerously represented by individuals in high lati- 
tudes; some of them ‘are among the most arctic of mammals. 
Susp-FAMILY Murinz. 
The gencra of this sub-family are, by Dr. Coues, separated into two 
groups: tribe (1) Mures, of the Old World, with the tubereles of upper 
molars in three series, and the palate extending back of the molars; and 
(2) Sigmodontes, New World eenera, with the tubercles of upper molars 
in two series, and the palate ending opposite last molars. 
Of the tribe Mures, four species of the typical genus, Mus, are found in 
North America, viz.: M. decumanus, Pallas, the Brown or Norway Rat, 
introduced into North America about 1778, and now the commonest 
species; M. rattus, Linnzeus, the Black Rat, introduced about 1544, but 
now being supplanted by the preceding ; Af. alexandrinus, Geoff., the Roof 
Rat, or White-bellied Rat, introduced in the southern States; and M. 
musculus, Linneeus, the cosmopolitan House Mouse. These pests are 
among the best known of mammals, but, not being indigenous to the 
fauna of Ohio, are not treated in the present report. 
The tribe Sigmodontes, Coues, includes all the indigenous American 
Murine. Four genera are recognized; Neoloma, Sigmoedon, Ochetodon, and 
Hesperomys—the last with three sub-genera. 
Genus NeotoMaA Say and Ord. 
\) 
Mus, sp., Say and Ord, 1818-23.—Desmarest, 1822. 
Arvicola, sp., Harlan, 1825. 
Lemmus, sp., Fischer, 1829. 
