368 PROCEEDINGS OF THE NATIONAL MUSEUM VOL, 92 
scales on posterior surface of thigh and on sides of neck minute or not; 
dorsals as long as broad or broader, with well-defined keels; adults gen- 
Crall ye DLO WAU SOT P18 yee ea ate eae eel yg eee ed me ve 
2.0 Series Of projecting scales above ear... eee eee 3 
INO SPEOJCCLIN SY SCALES AW OVE MeL eee ene ate ee eae oe ee 4 
8. Scales above ear short, obtusely conical; an azygous prefrontal; central 
Chiapas: (mean Comite) ose ee oe oa a a ochoterenai 
Scales above ear very elongate; no azygous prefrontal; all scales between 
frontal and rostral paired; central Chiapas, Guatemala________ fimbriatus 
4. Suboculars missing or reduced to minute scales; only one anterior temporal 
borderine) orbit? central Guerreros 222-2 a =a ae ene a deppii 
Suboculars present ; two anterior temporals bordering orbit______________ 5 
5. Area of granules on sides of neck very narrow; no granular zone in lateral 
fi) ies St ate Ne ote 8 ss Bee NL Lee Ae Bae i eee ee oaxacae 
Area of granules covering entire sides of neck; a granular zone in lateral 
ch) ee a re ae ce ee lee ee 
6. Dorsals larger, 25 to 29 from interparietal to posterior margin of thighs; 
scales across nape usually reduced to 4 or 5 in at least 1 transverse row; 
central) Veracruziand adjacent PueblaLos == 2222222 se ee gramineus 
Dorsals smaller, 82 to 34 from interparietal to posterior margin of thighs; 
seales across nape not reduced to less than 6 in any transverse row; south- 
erm Hidalzo, central and northern (Puebla2-—2222 2 eae ee taeniatus 
7. Supranasal plates absent or fused with first pair of internasal seales; nasal 
in contract with rostral; a large azygous prefrontal; western Chihuahua, 
probablyjeastern: Sonora_-- = == sss (caeruleus group)___~ kingii 
Supranasal plates present, small or, if enlarged, forming the second pair 
of scales behind rostral; nasal rarely in contact with rostral; a large 
NZVZOUS Prefrontal ON MOUs 22 = ee ee ee ee 8 
8. Posterior inner (usually outer also) supraocular in contact with orbit; super- 
ciliary series short, only anterior portion present (rarely posterior portion 
present, separating two posterior supraoculars from orbit); rarely an 
azygous prefrontal, minute when present; dorsals from interparietal to 
posterior margin of thighs 27 to 50_-_-----_____ imbricatus group____  $ 
Posterior supraoculars separated from orbit by a complete series of super- 
ciliaries; an azygous prefrontal or not; dorsals not less than 45__-__- 14 
9. Longitudinal rows of dorsals: 14 or less_-._--—_====-= =e Hee reeds eae ttes 5 OH es 10 
onvitudinal rows Of dorsals (16 2- ee 12 
10. Dorsal scales less than 35 (27 to 29) ; western Mexico (State)____ rudicollis 
WMorsal:scales.35 (0 4322222 * oes ee ee ee ee a ee eee 11 
11. Rows of dorsals 12; western Mexico (State), perhaps adjacent Michoacin 
andy Guana juatos. = ee eee ee imbricatus adspersus 
Rows of dorsals 14; Oaxaca highlands and southern edge of central plateau 
in Michoacan-east'to Veracruz 2=—2— 22" eee imbricatus imbricatus 
12. Only median superciliary plate present; preocular in contact with anterior 
supraocular; western Chihuahua, and probably adjacent areas in Sonora 
DTN LPS) WANN Oe ae ee eee levicollis levicollis 
At least an anterior as weil as median, and generally a total of three 
superciliaries ; preocular rarely in contact with anterior supraocular__ 13 
13. Head scales perfectly flat (c.f. gadovii et al.) ; Oaxaca_-________ planifrons 
Head scales convex; southern Coahuila to northern Guanajuato, central 
Durango to Sanus) Potosizes 22s eee eee eee levicollis ciliaris 
14. Two large loreals, one following the other (sometimes the posterior split 
into several scales) ; last two supralabials low, nearly straight-edged above 
(not angular) ; body and tail very elongate________ liocephalus group. 20 
