The eastern pipistrelle, _Pipistrellus subflavus_ (Cuvier) in the western part of its range, occurs along the Río Grande and its tributaries as far west as northern Coahuila and Val Verde County, Texas. Specimens from those places represent a heretofore undescribed subspecies which may be named and described as follows:

#Pipistrellus subflavus clarus new subspecies#

_Type._–Female, adult, skin and skull; No. 48270, Univ. Kansas Mus. Nat. Hist.; 2 mi. W Jiménez, el. 850 ft., Coahuila; 19 June 1952; obtained by Rollin H. Baker, original No. 2062.

_Range._–Known from northern Coahuila and adjacent parts of southwestern Texas.

_Diagnosis._–Size large (see measurements); upper parts pale, near (_c_) Cinnamon-Buff (capitalized color term after Ridgway, Color Standards and Color Nomenclature, Washington, D. C., 1912); skull large; zygomata expanded laterally.

_Comparisons._–Compared with _Pipistrellus subflavus subflavus_ (specimens from Marshall Hall in Maryland, Raleigh in North Carolina, and Barber County in Kansas) _P. s. clarus_ is paler, of approximately equal size, and has the zygomata slightly more expanded laterally. From _Pipistrellus subflavus veracrucis_ (Ward), specimens from 4 km. E Las Vigas, el. 8500 ft., Veracruz, _P. s. clarus_ differs in being larger, paler, and in having a larger skull.

_Remarks._–_Pipistrellus subflavus clarus_ is the palest subspecies of the eastern pipistrelle. Of the specimens assigned to _clarus_ (all taken in May and June), only two are sufficiently dark to compare favorably with examples of typical _subflavus_. A specimen (KU 60296) assigned to _P. s. subflavus_ from Rancho Pano Ayuctle, el. 300 ft., 6 mi. N Gómez Farías, Tamaulipas, is much darker than _clarus_. A specimen recorded from Devils River, Texas, by V. Bailey (N. Amer. Fauna, 25:211, October 24, 1905) has not been examined by me but presumably is _P. s. clarus_.