86 BULLETIN IS 7, UNITED STATES NATIONAL MUSEUM 



Megalops Hallowell (nee Lacep^de), Proc. Acad. Nat. Sci. Philadelphia, vol. 

 12, 1860 (1861), p. 188 (type, M. macMlafa Hallowell). 



Leptodira Cope, Proc. Acad. Nat. Sci. Philadelphia, vol. 18, 1866, p. 127 (emen- 

 dation ; type, Coluber annulatus Linnaeus). 



Anoplophallus Cope, Amer. Nat., vol. 27, 1893, p. 480 (substitute for Megalops 

 Hallowell, preoccupied; type, M. maculata Hallowell). 



Genotype. — CoUiber annulatus Linnaeus. 



Range. — Extreme southern Texas and Sonora south on both coasts 

 into South America. 



Species. — Sixteen species and subspecies occur in Central America 

 and Mexico; 13 occur in Mexico. Several other species are known 

 from South America. 



KEY TO MEXICAN FORMS OF LEPTODEIRA 



1. Most of dorsal bands involving extreme tips of ventrals 2 



Few if any dorsal bands involving tips of ventrals 5 



2. Bands on body over 16 (18 to 30) 3 



Bands on body less than 17 (10 to 15) 4 



3. Bands narrowly separated from each other, medially by less than one 



scale length, laterally by one and one-half frenata 



Bands more widely separated from each other yucatanensis yucatanensis 



4. Anterior and posterior edges of bands irregularly diagonal, seldom 



straight, ventrals 166 to 173 smithi 



Anterior and posterior edges of bands nearly straight, vertical ; ventrals 

 187 to 196 mystacina 



5. Ventrals over 192 6 



Ventrals less than 192 8 



6. Bands reaching second scale row or farther at least posteriorly. 



annulata septentrionalis 

 Bands seldom reaching as far as third scale row 7 



7. Bands on body 49 or more annulata polysticta 



• Bands on body 47 or less annulata taylori 



8. Dorsal spots very small and numerous, about as long as a scale ; ventrals 



149 to 164 punctata 



Dorsal spots larger ; ventrals 160 or more 9 



9. A middorsal, longitudinal dark stripe or spot on nape 10 



No such mark ; usually a narrow, light collar maculata 



10. Dorsal bands on body reaching first or second scale row 12 



Dorsal bands on body not extending beyond third scale row 11 



11. Dorsal bands 19 to 25 on body splendida 



Dorsal bands 32 to 38 on body bressoni 



12. Preoculars generally two, sometimes one; one or two distinct, light- 



edged, oval dark spots on each parietal yucatanensis malleisi 



Preoculars three ; no distinctly outlined dark spots on parietal 13 



13. Ventrals 186 to 197; posterior scale rows generally 15 or 16, rarely 17; 



median nape stripe redi:ced to an elongate spot at posterior edge of 

 parietal ; lateral spots dim or absent ; postocular stripe dim, not nearly 



reaching first dorsal blotch annulata septentrionalis 



Ventrals fewer, 180 to 182 ; posterior scale rows 17 ; a longitudinal nape 

 stripe extending from posterior tip of parietals to first dorsal blotch ; 

 lateral spots and postocular stripes more distinct ephippiata 



