Hibbard (1944:719) recovered _S. cinereus_ and a species of _Neosorex_ (a name formerly applied to the water shrew) from the Pleistocene (late Kansan) Cudahy Fauna. This indicates that the ancestors of the modern _S. cinereus_ and of the water shrew had diverged from one another before that time. Brown (1908:172) recorded _S. cinereus_ and _S. obscurus_ from the Conard Fissure in Arkansas. These materials were deposited probably at a later time than was the Cudahy Fauna. The _S. obscurus_ from Conard Fissure probably represents the ancestral _S. vagrans_ stock which I think reached eastern United States in Illinoian time and gave rise to _S. longirostris_. The Conard Fissure material was deposited at a time (Illinoian?) when northern faunas extended farther south than they do today. All of the species mentioned as having structural characters in common with _S. vagrans_ seem to have arisen from a common ancestor which had already differentiated from the ancestor of such species as _S. arcticus_, _S. saussurei_, and others. Consequently all are here included in a single subgenus. The oldest generic name applied to a shrew of this group, other than the name _Sorex_, is _Otisorex_ DeKay, 1842, type species _Otisorex platyrhinus_ DeKay, a synonym of _Sorex cinereus_. The subgenus can be characterized as follows. Subgenus =Otisorex= DeKay 1842. _Otisorex_ DeKay, Zoology of New York, pt. 1, Mammalia, p. 22, and pl. 5, fig. 1. Type, _Otisorex platyrhinus_ DeKay (= _Sorex cinereus_ Kerr). Third unicuspid usually smaller than fourth; upper unicuspids usually with pigmented ridge extending from apices medially to cingula, uninterrupted by antero-posterior groove; post-mandibular foramen usually absent. Includes the species _S. cinereus, S. longirostris, S. vagrans, S. ornatus, S. tenellus, S. trigonirostris, S. nanus, S. juncensis, S. willeti, S. sinuosus, S. veraepacis, S. palustris, S. bendiri, S. alaskanus_, and _S. pribilofensis_. [Illustration: FIGS. 11-14. Characters of the subgenera _Sorex_ and _Otisorex_. FIG. 11. Medial view of right ramus of _Sorex (Otisorex) vagrans_. x 14. FIG. 12. Medial view of right ramus of _Sorex (Sorex) arcticus_. x 14. FIG. 13. Anterior view of left second upper unicuspid of _Sorex (Otisorex) vagrans_. x 45. FIG. 14. Anterior view of left second upper unicuspid of _Sorex (Sorex) arcticus_. x 45.]