align="right">41.8

40.4-44.5 " " " ♀ 6 42.1 40.7-43.4 Condylobasal length ♂ 16 15.5 15.1-15.8 " " ♀ 5 15.4 15.1-15.8 Interorbital breadth ♂ 16 4.0 3.8-4.2 " " ♀ 5 3.9 3.9-4.0 Mastoid breadth ♂ 16 8.2 7.8-8.6 " " ♀ 5 8.3 8.0-8.5 Zygomatic breadth ♂ 15 10.4 10.2-10.7 " " ♀ 5 10.4 10.1-10.6

Remarks.—Miller and Allen (op. cit. :90) considered specimens of Myotis velifer from Roosevelt, Arizona, to be intergrades between M. v. velifer and M. v. incautus because the color varied greatly and certain pale individuals resembled incautus. These workers regarded specimens from southern Arizona as nearly typical examples of M. v. velifer. I have examined the specimens from Roosevelt, Arizona, and many from various localities in the southern part of the state, and was impressed by the large amount of color variation. Marked variation in color at a single locality, however, is known in other bats. Benson (Jour. Mamm., 30:50, February 14, 1949), for example, found striking variation in Myotis volans in California. The specimens of Myotis velifer from Roosevelt, Arizona, referred to M. v. velifer by Miller and Allen (op. cit. :90), actually average significantly smaller than specimens of this subspecies from Mexico, and than specimens of the large subspecies M. v. incautus from the Great Plains, and therefore, with reference to size, are not intergrades between these subspecies. All of the Arizonan material is here referred to M. v. brevis.

The "bald spot," that is to say, the sparsely furred area between the shoulders, which is characteristic of this species, reaches its most extreme condition in Myotis velifer brevis. In most of thirty-five specimens taken in mid-June, 1953, in California, the nape of the neck, the interscapular area, and a connected area extending laterally onto each shoulder are so lightly furred that the skin shows through conspicuously. In one male of this series a strip approximately four millimeters wide extending along the mid-dorsal line from between the shoulders to the rump is mostly devoid of hair. These sparsely-furred areas are less evident in live animals than in study skins and specimens in alcohol, because the back of the head in life lies against the depression between the shoulders and conceals most of the thinly furred areas.

The pelage of Myotis velifer brevis is shorter than that of either M. v. velifer or M. v. incautus and gives the impression of being less dense. The dorsal hairs average approximately 4.5 millimeters long in M. v. brevis taken 35 miles north of Blythe, Riverside County, California, in May, eight millimeters in M. v. velifer collected at Las Vigas, Veracruz, in January, and six