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 millimeters in _M. v. incautus_
taken four and one half miles so