narrower; mesopterygoid fossa broader; auditory bulla slightly smaller; upper parts distinctly darker.

Remarks.—N. a. subsolana is characterized by the combination of small size, dark color, small auditory bulla and relatively broad braincase. Typical specimens have been collected only at higher elevations in the Sierra Madre Oriental where no other species of Neotoma is known to occur.

Intergradation between N. a. subsolana and N. a. leucodon occurs at lower elevations on the west side of the Sierra Madre Oriental as shown by specimens from nine miles southwest of Tula, Tamaulipas, and Sierra Guadalupe, Coahuila, from which places some specimens are paler than others, approaching leucodon in color, and are slightly larger than typical subsolana. Specimens assigned to leucodon from vicinity of Presa Guadalupe and from 1 to 6 kilometers south of Matehuala, San Luis Potosí, are typical of that subspecies in measurements but are darker than topotypes.

N. a. subsolana intergrades with N. a. albigula in southeastern Coahuila (specimens from 6 to 9 miles east of Hermanas and from Panuco) where some individuals average paler and smaller than topotypes of subsolana and some have skulls that combine characters of subsolana and albigula. These specimens, which were referred to N. a. leucodon by Baker (Univ. Kansas Publ., Mus. Nat. Hist., 9:281-282, June 15, 1956), are assigned to subsolana on the basis of relatively dark upperparts and broad mesopterygoid fossa (narrow in only one specimen).

On geographic grounds, specimens not studied by me from Municipio de Galeana, Nuevo León (Koestner, Great Basin Nat., 2:13, 1941), and those from Jaumave, Tamaulipas (Goldman, N. Amer. Fauna, 31:37, October 19, 1910), probably are referable to N. a. subsolana.

The subspecific name subsolana (Latin adjective for eastern) is proposed for this woodrat because of its eastern geographic occurrence.