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 <strong>Mountain</strong>s 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 <strong>Mountain</strong>s 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,
90 BULLETIN CARNEGIE MUSEUM OF NATURAL HISTORY NO. 32 33 32 31 30 29 28 L 114 113 112 111 110 109 Gulf of California 114 113 112 111 110 109 Fig. 49.-Geographic distribution of Crofaphytus nebrius. The cross-hatched area represents the distribution of C. dickersonae. C. nebrius occurs throughout the north-south trend- tains, as well as the Buckeye Hills. They are also ing mountain ranges, with specimens known from known from a few mountain ranges further to the the Gila, Mohawk, Little Ajo, Ajo, Pozo Redondo, east including the Quijotoa, Silverbell, and Tucson Pueno Blanco, Sikort Chuapo, and Estrella moun- mountains (C. collaris occurs on the opposite side
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