Ticul Alvarez

“ 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. ”

“ Comparisons.—Neotoma albigula subsolana, differs from topotypes of N. a. leucodon, the subspecies geographically adjacent to the southwest, as follows: size smaller, especially length of palatal bridge (6.9-8.1 instead of 8.2-9.6) , alveolar length of maxillary tooth-row (8.3-8.9 instead of 8.8-9.7) , and greatest length of auditory bulla (7.3-7.9 instead of 8.2-8.9) ; mastoid breadth relatively greater, 51.1 (47.8-52.7) instead of 47.0 (45.5-49.1) per cent of basilar length; posterior process of premaxilla extending only slightly beyond posterior border of nasals ”

“ 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. ”