populations rests upon a reasonable, but as
yet unproved, assumption that intergradation occurs. Although Zweifel
examined specimens of the nominal subspecies from the upper Balsas
Basin, he did not study specimens from the intervening area--the
Tepalcatepec Valley in Michoacan.

Field studies and the examination of large series of preserved
specimens of _Cnemidophorus_ from the Tepalcatepec Valley show the
presence of _Cnemidophorus sacki_ in the region between the ranges of
_C. sacki sacki_ in the upper Balsas Basin and _C. sacki occidentalis_
in Jalisco and southern Nayarit. Furthermore, the populations of
_sacki_ inhabiting the Tepalcatepec Valley have characters of
scutellation and coloration that distinguish them from other described
subspecies of _sacki_. In recognition of the important contributions
to the systematics of the genus _Cnemidophorus_ made by Dr. Richard G.
Zweifel, I propose that the subspecies of _Cnemidophorus sacki_ in the
Tepalcatepec Valley be named as follows:

+Cnemidophorus sacki zweifeli+ new subspecies

_Holotype._--University of Michigan Museum of Zoology No. 119542, from
Capirio, Michoacan, Mexico (185 meters), an adult male, one of a
series collected on June 13, 1958, by William E. Duellman, Jerome B.
Tulecke, and John Wellman. Original number WED 12310.

_Paratopotypes._--UMMZ Nos. 119536-119541 and 119543-119550.

_Diagnosis._--A race of _Cnemidophorus sacki_ characterized by large
size (more than 130 mm. snout-vent length in males), approximately 106
dorsal granules around the midbody, about 41 femoral pores, and a
dorsal color-pattern in adult males consisting of lateral and
dorsolateral rows of spots, paravertebral rows fused with middorsal
light green area at least anteriorly, and pink throat having a median
light blue spot or transverse band.

_Description of Holotype._--Snout-vent length, 128 mm.; tail length,
252 mm.; tail/body ratio, 1.97; scutellation typical of _sacki_--four
supraoculars, enlarged postantebrachials, and enlarged mesoptychials;
107 granules around midbody (excluding enlarged ventrals); 45 femoral
pores; three enlarged preanal scales; supraorbital semicircle-series
extending anteriorly to posterior edge of frontal (Fig. 1).

[Illustration: Top View Head - Cnemidophorus sacki zweifeli]

~Fig. 1.~ Top view of the head of the holotype of _Cnemidophorus sacki
zweifeli_ (UMMZ 119542) showing scutellation. x5.

Top of head and na