Comparison of the Pleistocene specimens with specimens of Recent species of North American _Sorex_ reveals that the presence or absence of the post-mandibular foramen is almost constant in any one species. In possessing this foramen the fossils differ from most individuals of the species: _Sorex cinereus_, _S. pacificus_, _S. milleri_, _S. vagrans_, _S. obscurus_, _S. ornatus_, _S. fumeus_, _S. palustris_, _S. bendirii_, and _S. veraepacis_. The fossils differ from all these species in other characters as well; consequently detailed comparisons with them need not be made here. Species which possess the post-mandibular foramen include _Sorex saussurei_, _S. merriami_, _S. trowbridgii_, _S. arcticus_, _S. tundrensis_, and _S. sclateri_. _Sorex merriami_ differs in smaller size, smaller and weaker dentition, relatively higher coronoid, and relatively deeper and shorter dentary. _Sorex trowbridgii_ is similar to the fossils and to _S. saussurei_. Differences between the jaws of _S. trowbridgii_ and _S. saussurei_ seem to me to be differences of size only. _Sorex sclateri_ is larger than the fossils and m2 is longer in relation to m1, being almost the same size as m1. In the fossils m2 is noticeably shorter than m1, owing to close appression of the hypoconid and protoconid and in general to a smaller talonid area. _Sorex arcticus_ differs in larger incisor and p4. _Sorex tundrensis_ differs in relatively narrower molars. I have compared the fossils also with the Pliocene and Pleistocene _Sorex taylori_ Hibbard, and find that the fossils are larger and have larger teeth and a much wider separation of the protoconid and metaconid. I can find no significant way in which the fossils differ from _S. saussurei_. This of course implies similarity to _S. trowbridgii_. Since _S. saussurei_ is a widespread species in México today and since it occurs in the vicinity of the San Josecito area the specimens under discussion are referred to this species. Cryptotis mexicana (Coues)