_Diagnosis._--Yellowish-brown with an overlay of grayish anterior to the shoulders; forearm, 42.7-47.2. _Remarks._--Specimens from Baja California and the adjacent western part of the mainland of Mexico average paler than specimens from Veracruz and some places in Central America but the differences are slight. _Records of occurrence._--Specimens examined, 21, as follows: BAJA CALIFORNIA.--Comondu, 1 (USNM); Sierra Laguna, 4 (1 USNM, 3 British Mus.). COAHUILA.--4 mi. W Hacienda La Mariposa, 2300 ft., 2 (KU). ZACATECAS.--Concepcion del Oro, 7680 ft., 4 (KU). TAMAULIPAS.--Sierra de Tamaulipas, 1200 ft., 10 mi. W, 2 mi. S Piedra, 5 (KU); 16 mi. W, 3 mi. S Piedra, 1 (KU). SINALOA.--1 mi. S Pericos, 1 (KU). VERACRUZ.--Achotal, 1 (Chicago Mus.). YUCATAN.--Yaxcach, 1 (USNM). COSTA RICA.--Lajas, Villa Quesada, 1 (AMNH); San Jose, 1 (AMNH). _Additional records:_ CALIFORNIA: Palm Springs (Constantine, 1946:107). ARIZONA: Tucson (Cockrum, 1961:97). BAJA CALIFORNIA (Handley, 1960:474): Santa Ana; Miraflores. SINALOA: Escuinapa (Handley, 1960:475). DURANGO: Aguajequiroz, 12 mi. SSW Mapimi, 5000 ft. (Greer, 1960:511). SAN LUIS POTOSI (Dalquest, 1953:62): 1-1/2 mi. E Rio Verde; 19 km. SW Ebano; 4 mi. SSW Ajinche. QUINTANA ROO: 7 mi. N, 37 mi. E Puerto de Morelos (Ingles, 1959:384). HONDURAS: Tegucigalpa (Handley, 1960:474). Lasiurus ega panamensis (Thomas) 1901. _Dasypterus ega panamensis_ Thomas, Ann. Mag. Nat. Hist., ser. 7, 8:246, September, type from Bogava [= Bugaba], Chiriqui, 250 meters, Panama. 1960. _Lasiurus ega panamensis_, Handley, Proc. U.S. Nat. Mus., 112:474, October 6. _Geographic distribution._--Panama; also recorded by Handley (1960:474) from Venezuela. _Diagnosis._--"General colour dark brownish clay-color, something between Ridgway's 'raw-umber' and 'clay-color'. Fur black basally, then dull brownish buffy, the extreme tips black. Center of face similar to back, cheeks from eyes to lips contrasting black. Rump and hairy part of interfemoral verging toward brownish fulvous. Under surface similar to upper." (Thomas, 1901:246.) Forearm of holotype, 46.5. _Remarks._--Notes taken down by one of us (Hall) on July 16, 1958, at the British Museum, Natural History, contain the following: "Color accurately described by Thomas. The blackish stands out. The difference between the types of _D. e. panamensis_ and _D. e. xanthinus_ is tremendous." _Record of occurrence._--Specimen examined, one, the type (British Mus.). RELATIONS BETWEEN THE SPECIES OF LASIURUS