1896. _Lepus sylvaticus holzneri_ Mearns, Proc. U.S. Nat. Mus.,
18:554, June 24.
1904. _Sylvilagus floridanus holzneri_, Lyon, Smithsonian Miscl.
Coll., 45:336, June 15.
Examination of cottontail rabbits from Arizona in the Biological Surveys
Collection and the United States National Museum indicates that
_Sylvilagus audubonii_ can be distinguished from _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 Hualpai Mountains, Pine
Springs, and Prescott under the name _Sylvilagus nuttallii pinetis_.
Nelson (_op. cit._:Pl. X, fig. 2) figured one of these skulls from the
Hualpai Mountains as _S. n. pinetis_ and the cranial measurements (_op.
cit._:201) that he records for _S. nuttallii pinetis_ likewise are of
these same specimens of _Sylvilagus floridanus holzneri_. Nelson's
description (_op. cit._:207-210) seems to have been affected by the
erroneous (as we see the matter) inclusion of these specimens of _S. f.
holzneri_ in the materials identified by him as _Sylvilagus nuttallii
pinetis_.
The specimens so far mentioned from Arizona can be identified with ease.
The identification becomes difficult, however, when the holotype of _S.
f. holzneri_, from the Huachuca Mountains, is examined. The difficulty
results from the holotype having a barely detectable emargination in the
posterior border of the supraoccipital shield. In this respect the
holotype is intermediate between _S. f. holzneri_ (as known by specimens
from more western localities in Arizona) and _S. n. pinetis_ from the
White Mountains to the northward. As noted above, _S. f. holzneri_ has a
deep notch and _S. n. pinetis_ has none. This intermediacy of the
holotype supports the possibility, mentioned by Nelson (_op. cit._:200),
that intergradation occurs between _S. f. holzneri_ and _S. n. pinetis_.
Additional evidence, however, is against this possibility; the notch in
the supraoccipital is deeper in specimens (No. 66136, from Chiricahua
Mts., and No. 204364, from Ash Creek in Graham Mts.) from mountains
geographically intermediate between the Huachuca Mountains and the White
Mountains. Also, the holotype of _S. f. holzneri_ differs from _S. n.
pinetis_ and agrees with other specimens of _S. f. holzneri_ from
farther southwest in Arizona in the robustness of the posterior
extensions of the supraorbital processes and in the considerable degree
of fusion of the tips of these processes with the squamosals.
Additionally, the rostrum of the holotype is wide and deep as in other
specimens of _S. floridanus_ from more eastern localities and is unlike
the narrow and shallow rostrum of _S. n. pinetis_.
If intergradation occurs in Arizona between the species _Sylvilagus
floridanus_ and _Sylvilagus nuttallii_, as Nelson (_op. cit._:200)
intimated it might, the intergrades probably will be found along the
Tonto Rim or in the territory between the Blue Range and the Graham
Mountains.