BOID®. 73 
Lower labials with pits; nostril supero-l§jteral, in a semidivided 
ER Liasis, p. 76. 
2. Tail prehensile ; rostral and anterior upper labials deeply 
yh As 4, Python, p. 80. 
B. Premaxillary bone toothless. 
Palate toothed; labials pitted; tail prehensile, with two rows of 
eee Ee 5. Chondropython, p. 90. 
Palate toothed; no labial pits; tail not or but very slightly 
prehensile, with the subcaudals ‘mostly single, 
6. Aspidites, p. 91. 
Palate toothless; no labial pits; no mental groove; tail not pre- 
hensile ; subcaudals single ...... 7. Calabaria, p. 92. 
IL. No supraobital bone; no premaxillary teeth; subcaudals 
mostly single ...............- BOIN A. 
A. Head distinct from neck ; tail more or less prehensile. 
1, Anterior teeth very strongly enlarged. 
Seales smooth ; head with shields ; labials without or with shallow 
Baas wipes bine e sw Ve OOK 8. Epicrates, p. 93. 
Scales smooth ; labials withdeep pits. 9. Corallus, p. 99. 
Seales keeled ; no labial pits........ 10. Enygrus, p. 104. 
2. Maxillary and mandibular teeth gradually decreasing in 
size. 
a. No enlarged rostral shield ; scales strongly keeled. 
1h she. p. 109. - 
b. An enlarged rostral shield. 
a. Scales moderate, in 21 to 29 rows. 
One or two pairs of prefrontal shields, 12. Ungalia, p. 110. 
A large azygous prefrontal shield.... 13. Ungaliophis, p. 114. 
B. Scales very small. 
Scales smooth ; nasals in contact behind the rostral, 
14. Eunectes, p. 115. 
Seales smooth ; nasals separated by small scales ; tail short. 
15. Boa, p. 116. 
Scales keeled; nasals separated by a pair of internasals ; tail long. 
16. Casarea, p. 121. 
B. Head not distinct from neck; tail not or but slightly 
prehensile. 
1. Scales tri- or quinquecarinate ; snout with large shields ; 
rostral moderate.......... 17. Bolieria, p. 121. 
