panded to form vertical bars
(Fig. 2 D).

Large adult males (+- 120 mm. snout-vent length) have all of the
stripes fragmented into spots. The diffuse middorsal area is expanded
and encloses the paravertebral rows of spots. The pale spots present
in the dark fields in smaller individuals are either absent or fused
with spots resulting from the fragmentation of the stripes (Fig. 2 E).

_Sexual dimorphism._--Males attain a larger size (known maximum
snout-vent length of 132 mm., as compared with 114 mm. in females).
Males have larger but not more numerous, femoral pores, blue bellies,
and pink and blue throats, whereas females are unicolor creamy white
ventrally. The more nearly complete metamorphosis of color pattern
exhibited by adult males probably is correlated with their large adult
size. Large females retain complete lateral and dorsolateral stripes.
The jowls of breeding males are swollen.

[Illustration: Color Pattern Change Diagram]

~Fig. 2.~ Diagrammatic representation of ontogenetic change in color
pattern in _Cnemidophorus sacki zweifeli_: A--hatchling, 34 mm.
snout-vent length; B--juvenile, 55 mm. snout-vent length;
C--subadult male, 80 mm. snout-vent length; D--small adult male,
100 mm. snout-vent length; E--large adult male, 120 mm. snout-vent
length.

_Geographic variation._--No noticeable geographic variation in this
subspecies is evident in the series from the Tepalcatepec Valley.
However, lizards from eastern Michoacan (Chinapa, 6 km. N of Tafetan,
6 km. S of Tzitzio, and 19 km. S of Tzitzio) differ slightly from
those from the Tepalcatepec Valley; the eastern specimens have fewer
dorsal granules and femoral pores, and a higher ratio of dorsal
granules between the paravertebral stripes to the number of granules
around the body (see Tables 1-3). No large adult males are present in
the eastern series; the subadults and small adult males have color
patterns like lizards of similar size from the Tepalcatepec Valley.
The largest male from the east has a snout-vent length of 110 mm.,
rows of pale spots, and no trace of brown and tan cross-bars.
Specimens of _Cnemidophorus sacki sacki_ of equal size from Guerrero,
Morelos, and Puebla in the upper Balsas Basin have a tan dorsum with
dark brown cross-bars. The localities in eastern Michoacan are
intermediate geographically between the Tepalcatepec Valley and the
known range of the nominal subspecies in the upper Balsas