112. ATB ACTUS. 801 



B. Loroal at least twice as long as deep. 



1. Two pairs of chin-shields ; usually a single postocular. 



Scales in 15 rows ; pra)frontals as long 



as broad ; eight upper labials 4. vittatus, p. 304. 



Scales in 17 rows ; praef rentals as long 



as broad ; six upper labials 5. latifrontalis, p. 304. 



Scales in 17 rows ; praef rentals much 



longer than broad ; six upper labials. 6. longiceps, p. 305. 



2. A single pair of moderately broad chin-shields ; anal entire. 



a. Scales in 17 rows. 

 a. Two postoculars. 



* Prsefrontals a little broader than long. 



Ventrals 140; rostral broader than deep ; 



six upper labials 7. peruvianus, p. 305. 



Ventrals 143-158 ; rostral broader than 



deep ; seven upper labials 8. gueniJieri, p. 305. 



Ventrals 175-191 ; rostral nearly as 



deep as broad ; seven upper labials . . 9. bocourti, p. 306. 



** Praefrontals as long as broad; ventrals 146-161. 



Rostral once and a half as broad as deep ; 



frontal slightly broader than long . . 10. maculatus, p. 306. 

 Eostral nearly as deep as broad ; frontal 



as long as broad or a little longer .... 15. crassicaudatus, p. 310. 



*** Praefrontals a little longer than broad. 



Frontal as long as broad or slightly 



longer than broad ; loreal twice and 



a half to thrice and a half as long as 



broad ; ventrals 163-182 11. major, p. 307. 



Frontal a little longer than broad ; loreal 



twice as long as broad ; ventrals 100. 12. isthmicus, p. 307. 

 Frontal as long as broad or a little 



broader than long ; loreal twice and 



a half to thrice and a half as long as 



deep ; ventrals 143-160 13. baditis, p. 308. 



/3. A single postocular ; frontal longer than broad ; eight 

 upper labials 14. torquatus, p. 309. 



b. Scales in 15 rows. 



a. Snout obtuse ; ventrals 150-172 ; subcaudals 16-32. 



* Eight upper labials. 



Prsefrontals longer than broad; both 



postoculars in contact with temporal. 16. duboisi, p. 310. 



Prajfrontals as long as broad ; lower post- 

 ocular not in contact with temporal . . 17. occipitoalbus, p. 310. 



