154 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 91 



appears to be of highland origin. Accordingly, the fact that the 

 hiscutatus group may have a Central American, or at least a more 

 southerly, origin does not necessarily mean that the upsilon group 

 is a derivative of it, since it occurs toward the north in the general 

 direction of migration of the hiscutatus group. In fact, the connec- 

 tion between the two groups is so remote that, were morphological 

 characters available, they would better be separated as different 

 genera. 



KEY TO THE GENUS TRIMORPHODON 



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



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



vilkinsojiii) 7 



2. Anal entire vandenburghi 



Anal divided 3 



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



with light color (or white) of ventral surface, but cut off iy the continua- 

 tion posteriorly of the black hand 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 the 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 connec- 

 tion indicated) lambda 



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

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



5. Blotches on body numerous (about 33), connected laterally in pairs. 



biscutatus quadruples 

 Blotches on body less numerous (25 or less) 6 



6. Blotches more than twice as long as spaces between ; no evidence middorsally 



of secondary bands or blotches paucimaculatus 



Blotches less than twice as long as spaces between ; usually secondary bands 

 or blotches present middorsally on some part of body. 



biscutatus biscutatus 



7. Anterior dorsal blotch covering 15 or more scale lengths on middorsal line, 



involving seven or more ventrals ; blotches usually gray or black 8 



Anterior dorsal blotch covering 13 or fewer scale lengths middorsally, in- 

 volving fewer than seven ventrals 9 



8. Blotches little narrower laterally than dorsally, much broader on belly than 



interspaces fasciolata 



Blotches much narrower laterally than dorsally, on belly equal to or narrower 

 than white interspaces latifascia 



9. Blotches very narrow, a third length of interspaces ; anterior border of first 



dorsal blotch 9 or 10 scales behind parietal vilkinsonii 



Blotches broader, little if any narrower than spaces between ; anterior 

 border of first dorsal blotch farther forward, not more than six scales 

 behind parietal 10 



10. Fifth and six labials entering orbit ; anterior loreal split, an upper and lower ; 



tail white, unmarked, below forbesi 



Fourth and fifth labials entering orbit; anterior loreal single; tail marked 

 below or not 11 



11. Bands on body 16 collaris 



Bands on body 22 or more 12 



