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spersed with numerous interstitial granules. Preo-
culars, suboculars, and postoculars form an arc of
five to ten rectangular scales, second, third, or fourth
scale only rarely elongate. Supralabials 1 1 to 17,
usually slightly longer than high except anteriormost
scale, which is square or pentagonal. Lorilabials in
one to three rows, ovoid to rectangular, juxtaposed,
separating supralabials from suboculars and nasals.
Aperture of external auditory meatus rectangular or
ovoid, often constricted at or above the midpoint,
approximately two to four times higher than wide,
with small, strongly convex, somewhat conical au-
ricular scales lining anterior margin. Mental pen-
tagonal, one to 1 .S times wider than high, bordered
laterally by anterior infralabials and posteriorly by
a pair of large postmentals. Postmentals usually not
separated from infralabials by sublabials; mental oc-
casionally contacted by one or two sublabials. Chin-
shields weakly differentiated or undifferentiated. In-
fralabials 13 to 17, square or wider than high, in-
ferior border convex. Gulars granular, strongly con-
vex and beadlike, each scale separated from adjacent
scales by numerous asymmetrically arranged inter-
stitial granules.
Dorsal scales in approximately 142 to 188 rows
midway between forelimb and hindlimb insertions.
Tail long, cylindrical or slightly laterally compressed
(oval) in both sexes and all age groups. Paired, me-
dian row of subcaudals larger than adjacent sub-
caudals and lateral caudals. Enlarged postanal scales
present in males.
Deep postfemoral dermal mite pocket present at
hindlimb insertion. Femoral pores 17 to 22, femoral
pores do not extend beyond angle of knee, separated
medially by 17 to 24 granular scales. Subdigital la-
mellae on fourth toe 17 to 20.
Coloration in Lve. -Dorsal body coloration is
generally straw yellow, although this is subject to
some intraspecific variation with some individuals
dull tan in color. Contrary to Stebbins (1985), the
anterior portion of the head may bear yellow pig-
ments similar to those present in some populations
of C. collaris. The white component of the dorsal
pattern is composed of white spots on the body that
are often roughly three times larger middorsally than
they are laterally. Spots or a broken reticulum may
be present on the tail and hindlimbs, while the forc-
limbs are generally spotted or mottled. Transverse
body bars are absent. Reticulations may be absent
entirely, confined to the superficial mandibular and
temporal regions, or present on these regions as well
OF CROTAPHYTID LIZARDS
as the hindlimbs below the knee. A broad white or
off-white caudal vertebral stripe is lacking. The dor-
sal surface of the head is usually pale-colored, and
is conspicuously patternless. Burnt orange ventro-
lateral coloration may be present in males, partic-
ularly those from the western portion of the species'
distribution, and may be a form of breeding col-
oration. The gular coloration in males is generally
slate gray or dark brown, but may be overlain with
a yellow tint. A black central gular component is
not present. The peripheral gular pattern is highly
variable in this species, with the Tucson Mountains
population characterized by the standard reticulated
pattern, western populations characterized by
obliquely oriented, radiating white stripes, and the
remaining eastern and southern populations char-
acterized by white spots on a sky blue background.
Anterior and posterior collar markings are always
present and the posterior markings may contact
middorsally. The anterior collars are complete ven-
trally in adult males, with black pigments extending
through the gular fold. A pair of black nuchal spots
may be present middorsally between the anterior
collar markings. A pair of enlarged melanic axillary
patches are variably present immediately posterior
to the forelimb insertion. Small melanic inguinal
patches are always present in adult males. The fem-
oral pores are generally off-white to gray in color.
Paired, melanic keels are always present on the ven-
tral surface of the caudal extremity, except in the
Tucson Mountains populations where they are lack-
ing in two of the three specimens examined.
Females are less vividly marked than males. The
dorsal coloration is often browner than that of males.
The head and gular markings are less vibrantly
marked and they lack male color pattern character-
istics such as the melanic inguinal patches, axillary
patches, and ventrally complete anterior collar
marking. Females develop vivid orange or reddish
lateral bars during the gravid period. The tail is not
vividly colored in adult or subadult females of this
species.
Size. -This species exhibits strong sexual dimor-
phism with males reaching larger adult size (maxi-
mum observed SVL = 1 12 mm) than females (max-
imum observed SVL = 98 mm).
Disrribution (Fig. 49). - Crotaphytus nebrius oc-
curs in lowland desert and arid-tropical thornscrub
mountain ranges of the Sonoran Desert where it
appears to be allopatrically distributed with respect
to all other Crotaphytus. In southwestern Arizona,