The first specimens of _Myotis velifer_ from California were taken in 1909 by C. L. Camp at Needles, San Bernardino County (Grinnell, Univ. California Publ. Zool., 12:266, March 20, 1914), and subsequently this bat was recorded from farther south in the lower Colorado River Valley at the Riverside Mountains, Riverside County (Stager, Jour. Mamm., 20:226, May 14, 1939). West of the Rocky Mountains the species is known to occur also in at least the southern two-thirds of Arizona, southwestern New Mexico, and is recorded from Thistle Valley, Utah, on the basis of two young specimens in alcohol (Miller and Allen, Bull. U. S. Nat. Mus., 144:87, May 25, 1928). Through comparisons made possible by the acquisition, in the last few years, of mammals from many parts of Mexico by the Museum of Natural History of the University of Kansas, it became evident that _Myotis velifer_ in California and Arizona was an heretofore unnamed subspecies.