134 



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. 



Arvicolinse. — Molars normally rootless (except in Evotomys), 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 mandible 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 

 aad 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. 



Sub-family MueinA. 



The genera of this sub-family are, by Dr. Coues, separated into two 

 groups: tribe (1) Mtires, of the Old World, with the tubercles of upper 

 molars in three series, and the palate extending back of the molars; and 

 (2) Sigmodontes, New World genera, 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.ratlus, Linnaeus, the Black Rat, introduced about 1544, but 

 now being supplanted by the preceding ; M. alexandrinus, Geoff., the Roof 

 Rat, or White-bellied Rat, introduced in the southern States; and M. 

 viusculus, Linnjeus, 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 

 Murinss. Four genera are recognized ; Neotoma, Sigmodon, Ochetodon, and 

 Hesperomys — the last with three sub-genera. 



Genus Neotoma Say and Ord. 



Mus, sp.. Say and Ord, 1818-23.— Desmarest, 1822. 

 Arvicola, sp., Harlan, 1825. 

 Lemmus, sp., Fischer, 1829. 



