CHECKLIST OF THE SNAKES OF MEXICO 145 



Genotype. — Tretanorhinus varidbilis Dumeril, Bibron, and Dnmeril. 



Range. — Extreme southern Mexico to Colombia and Ecuador, Cuba, 

 Isla de Pinos, and Caymans. 



Species. — Three species (one with two races) are recognized in 

 Central and South America; four others occur in the West Indies. 

 One occurs in Mexico. 



TRETANORHINUS NIGROLUTEUS LATERALIS Bocourt "9 



Tretanorhinus lateralis Bocoxn^x. Le Natiiraliste, ser. 2. No. lOl, 1801, p. 122. 

 Tretanorhinus nigrohiteus lateralis Dunn, Copeia, 1039, No. 4, p. 216. 



Type. — Mus. Hist. Nat. Paris. 

 Type locality. — Belize. 



Range. — Known onl_y from the type locality, Peten (Guatemala), 

 and Pacaitun, Rio Candelaria, Campeche. 



Genus TRIMORPHODON Cope 



Trimorpliodon Cope, Proc. Acad. Nat. Sci. Philadelphia, vol. 13, 1861, p. 297. — 

 Taylor, Uiiiv. Kansas Sci. Bull., vol. 25, 1938 (1939), pp. 357-383, fig. 1, 

 pis. 35-36, 38.— Smith, Proc. U. S. Nat. Mus., vol. 91, 1941, pp. 149-168, figs. 

 37-38. 



Eteirodipsas Jan, Elenco sistematico degli Ofidi, 1863, p. 105 (type, Dipsas 

 biscutata Dumeril, Bibron, and Dumeril). 



Genotype. — Lycodon lyrophanes Cops. 



Range. — Southern California to western Texas, south on the Pacific 

 coast and on the central plateau of Mexico, reaching Costa Rica. 



Species. — Fourteen species and subspecies are recognizable ; the only 

 •extralimital form is T. hiscutatus quadruplex. 



KEY TO MEXICAN FORMS OF TRIMORPHODON 



1. (Large V-shaped marks on head and nape 2 



No such marks; a transverse nuchal collar (or whole neck light, as in 



vilkinsonii) 6 



2. Anal entire vandenburghi 



Anal divided 3 



3. Light V-shaped mark, which involves parietals, not confluent postero- 



laterally with light color (or white) of ventral surface, but cut off by 

 continuation posteriorly of black band that on the head precedes the 



light band lyrophanes 



Light mark extending posterolaterally direct to ventral surface, or at 

 least not cut off laterally by preceding dark band 4 



4. Ventrals less than 245; blotches on body relatively numerous (maximum 



34), about as broad as long, not connected laterally in pairs (nor such 



a connection indicated) lambda 



Ventrals more than 245 ; blotches on body numerous or few, but if the 

 former, connected laterally in pairs (or such a connection indicated) — 5 



"Jan's Tretanorhinus variabilis adnexus (Elenco sistematico degli Ofidi, 1863, p. 67), 

 said to be from "Mexico," is based upon a specimen of a species known otherwise only from 

 Cuba ; the locality cited obviously is erroneous. 



