Sorex oreopolus emarginatus Jackson.—A first-year female Sorex, KU 54346, obtained by Rollin H. Baker from 7 mi. SW Las Adjuntas, 8900 ft., Durango, seems closest, among Mexican shrews that I have examined, to two specimens of S. emarginatus from Plateado, 7600 to 8500 ft., Zacatecas. Measurements of the Las Adjuntas specimen are: total length, 88; tail, 39; hind foot, 13; palatal length, 7.2; maxillary tooth-row, 6.4; maxillary breadth, 4.9; least interorbital breadth, 3.6.
Sorex emarginatus previously was known only from Plateado and the type locality, Bolanos, Jalisco. Comparison of these three specimens with specimens of other species of Mexican shrews of the S. saussurei group leads me to conclude that the group contains two species rather than four as was previously thought. Sorex emarginatus, S. ventralis, and S. oreopolus seem to me to be conspecific. All three nominal species are relatively small, short-tailed shrews. The skulls of the three kinds resemble one another in relatively short rostrum and in dental details. Slight differences in cranial proportions differentiate the three and they should, until more specimens of each are obtained and studied, retain subspecific rank. The specific name, Sorex oreopolus Merriam 1892, should apply to the three kinds since it antedates the names ventralis and emarginatus. The two names last given, therefore, should stand as Sorex oreopolus ventralis Merriam and Sorex oreopolus emarginatus Jackson. The two species, the large S. saussurei, and the small S. oreopolus, as the latter is here understood, occur together over an extensive region in southern Mexico. In other parts of North America a large and a small species of Sorex often occur together in a given area.
The Las Adjuntas specimen was taken only 10 miles southwest of El Salto, Durango, the type locality of S. durangae Jackson. Jackson (1928:101) placed durangae in the Sorex vagrans-obscurus species group, but the two specimens available to him were second year adults with the teeth so much worn that diagnostic characters are not visible on them. I have examined these two specimens (United States Biological Surveys Collection 94539 and 94540) and find that in bodily and cranial proportions they resemble Sorex s. saussurei, and I so assign them.
Sorex milleri Jackson.—Koestner (1941:10) reported 5 Sorex from Cerro Potosí, near La Jolla, Municipio de Galeana, Nuevo Leon, as Sorex emarginatus. Comparison of 4 of these specimens (Chicago Museum of Natural History, 48227, 48228, 48229, 48230) with two S. emarginatus from Plateado, Zacatecas, and specimens of other species of Sorex indicates that the Cerro Potosí shrews differ in many features from emarginatus, but closely resemble, in size and cranial characters, a specimen (F. W. Miller, No. 20) of S. milleri from Sierra del Carmen, Coahuila, and seems to be referable to that species which was not named when Koestner (loc. cit.) recorded his specimen. The range of S. milleri is therefore extended southwestward to western central Nuevo Leon.
Comparison of S. milleri with specimens of other species of North American Sorex leads me to conclude that S. milleri is most closely related to S. cinereus Kerr, and should be included in the S. cinereus group rather than in the S. vagrans-obscurus group. Sorex cinereus and S. milleri are alike, and both differ from even the smallest S. vagrans in relatively long and narrow rostrum, narrow teeth, smaller skull, and in having the third upper unicuspid more often equal to or smaller than, rather than larger than, the fourth unicuspid.
I judge S. milleri to be a relict population of S. cinereus, isolated in the mountains of northeastern Mexico, probably in the late Pleistocene. Sorex cinereus reported from Pleistocene deposits in San Josecito Cave, Nuevo Leon (Findley, 1953:635), probably represents a population ancestral to the modern S. milleri. Sorex milleri should retain specific status because of constant cranial differences from S. cinereus, particularly relatively broader rostrum.
LITERATURE CITED
Baker, R. H.
1953. Mammals from owl pellets taken in Coahuila, Mexico. Trans. Kansas Acad. Sci., 56:253-254.
Bole, B. P., and P. N. Moulthrop.