om _Sylvilagus nuttallii_
and _Sylvilagus floridanus_ by the larger (more inflated) tympanic
bullae. Topotypes of _Sylvilagus nuttallii pinetis_ and other specimens
from Alpine, Mt. Thomas, Springerville, the Prieto Plateau at 9000 feet
on the south end of the Blue Range, and the Tunitcha Mountains are
characterized by a posteriorly pointed supraoccipital shield and a long,
wide space between the braincase and the posterior extension of the
supraorbital process. The cottontails with equally small tympanic bullae
from more western and more southern localities are referable to
_Sylvilagus floridanus holzneri_ on the basis of a posteriorly truncate
or emarginate supraoccipital shield and a narrower and shorter space
(usually a "foramen") between the braincase and the posterior extension
of the supraorbital process. In _S. f. holzneri_ the posterior end of
the posterior process fuses with the braincase whereas the posterior end
of this process in Arizonan specimens of _S. n. pinetis_ merely lies
against the braincase or projects free of it. In specimens from Arizona
the difference in shape of the posterior border of the supraoccipital
shield and the difference in size of the space between the braincase and
the posterior extension of the supraorbital process are the only
differences of taxonomic worth found by us. Many other features of the
skull, of color of pelage, and of size of external parts all fell within
the range of individual variation of a series of specimens from one
locality.

Specimens from the following localities in Arizona are referable to
_Sylvilagus floridanus holzneri_ (Mearns).

Hualpai Mts., Nos. 117461, 117462, 117488, 117490, 117495, 227735,
and 227832; Ft. Whipple, No. 214157; Prescott, No. 34667/46752;
Mayer, No. 247495; Reynolds Creek Ranger Station, Sierra Ancha
Mts., Gila Co., No. 247734; Fish Creek, Tonto National Forest, 2000
ft., No. 212833; north base Mt. Turnbull, 4500 ft., No. 214339; Ash
Creek, 6100 ft., Graham Mts., No. 204363; Pinery Canyon, 7500 ft.,
Chiricahua Mts., No. 247953; Thomas Canon, 2 mi. E Baboquivari
Mts., No. 244420; Pine Springs, 15 mi. south of Colorado Canon, No.
2425 Amer. Mus. Nat. Hist. On December 4, 1950, we removed the
skull of No. 2425 to more certainly ascertain the identity of the
individual.

The specimens listed above include those that Nelson (N. Amer. Fauna,
29:211, August 31, 1909) listed from the Hu