Coahuilan specimens, although assigned to _auriculus_, are slightly paler (upper parts (16) Ochraceous-Tawny; underparts (_e_) Light Buff) and have less abruptly rising foreheads than do the bats from Tamaulipas. In these features, the Coahuilan animals are somewhat intermediate between typical _auriculus_ and _evotis_. The bat from Nuevo León, in both color and degree of slope of forehead, is intermediate between those from Coahuila and those from Tamaulipas. A bat from Perote, Veracruz, identified as _Myotis evotis chrysonotus_ (J. A. Allen) [=_M. e. evotis_] by Miller and Allen (U. S. Nat. Mus., Bull. 144:118 and 120-121, May 25, 1928) is here assigned to _M. e. auriculus_. Measurements given by these authors indicate that this bat has a large skull, which is characteristic of this subspecies. Another specimen, similarly assigned by these authors and from the San Luis Mountains in northwestern Chihuahua, seems to be _M. e. evotis_, although the published measurements (_loc. cit._) show that this bat tends toward _auriculus_ in size of skull and mandible. All specimens were taken in mist nets stretched over water. Those from Coahuila were snared over a concrete water tank situated near the base of low hills in mixed mesquite and chaparral. In Nuevo León, one bat was netted over a small pond around which grew some low trees in an intermontane valley in the Sierra Madre Oriental. In Tamaulipas two bats were caught in a mist net stretched across a narrow, brush-bordered arroyo in the Sierra de Tamaulipas. One adult male weighed 7.0 grams; average and extreme weights of 7 adult, non-pregnant females were 6.8 (5.2-8.0). Females taken on March 25 and 26 were not pregnant; one obtained on June 20 was lactating. Funds for financing field work were made available by the Kansas University Endowment Association and the National Science Foundation. _Measurements._--Measurements, in millimeters, of the holotype and another female (No. 55111 KU) from the type locality and 3 females (Nos. 44726, 44729-30 KU) from Coahuila, respectively, are: total length, 94, 93, 97, 86, 96; length of tail vertebrae, 43, 42, 41, 39, 45; length of hind foot, 9.5, 9, 10, 10, 8; height of ear from notch, 20, 20, 20, 18, 20; length of forearm, 37.9, 38.4, 40.2, 37.3, 38.5; greatest length of skull, 16.1, 16.4, 16.2, 15.8, 16.1; condylobasal length, 15.4, 15.4, 15.6, 15.0, 15.4; zygomatic breadth, 9.7, 9.9, 10.1, 9.4, 9.9; least interorbital constriction, 3.9, 3.8, 3.9, 3.7, 3.7; breadth of braincase, 7.5, 7.6, 7.5, 7.5, 7.6; occipital depth, 5.9, 5.9, 5.5, 5.7, 5.6; palatal length, 8.5, 8.7, 8.7, 8.7, 8.9; mastoid breadth, 8.2, 8.4, 8.3, 8.2, 8.3; breadth across third upper molars, 6.1, 6.2, 6.3, 6.1, 6.1; length of maxillary tooth-row, 6.5, 6.5, 6.7, 6.6, 6.6; length of mandible, 11.5, 11.8, 11.9, 11.2, 11.7; length of mandibular tooth-row, 8.0, 8.0, 8.1, 8.1, 8.1.