530 VIPEEIDJ3. 



Porthidium, Cope, Proc. Ac. Philad. 1871, p. 207. 

 Atropophis, Peters, Ann. Mus. Oenova, iii. 1871, p. 41. 

 Ehinocerophis, Garman, Bull. Mus. Comp. Zool. viii. 1881, p. 85. • 

 Ophryacus, Cope, Bull. U.S. Nat. Mus. no. 32, 1887, p. 88. 

 Thanatopliis, Posada-Arango, Bull. Soe. Zool. France, 1889, p. 343. 



Upper surface of head covered witt scales or small shields. _ Body- 

 cylindrical or compressed ; scales smooth or keeled, with or without 

 apical pits. Tail moderate or short ; suhcaudals single or in two 

 rows. 



South-eastern Asia ; Central and South America. 



Synopsis of the Species. 



I. American species, with non-prehensile tail. 

 A. Suhcaudals all or greater part in two rows. 



1. Posterior suhcaudals replaced hy small scales ; upper head- 



scales granular, smooth or ohtusely keeled ; supraocular 

 shield narrow ; scales tubercularly keeled, in 35 or 37 

 rows ; ventrals 200-230 ; suhcaudals 32-50. 



1. mutus, p. 534. 



2. No small scales under the tail ; upper head-scales imbricate 



or subimbricate ; supraocular large. 



a. Scales on the vertex and occiput more or less strongly 

 keeled ; dorsal scales strongly keeled. 



a. Second upper labial forming the anterior border of the 

 loreal pit. 



* Xeels on the dorsal scales extending nearly to the 



extremity ; scales in 23-33 rows ; ventrals 180- 

 240 ; suhcaudals 46-70. 2. lanceolatus, p. 535. 



** Keels on the dorsal scales much shorter than the 

 scales. 



Scales in 25-29 rows ; ventrals 161- 



216 ; suhcaudals 47-73 3. atrox, p. 537. 



Scales in 21-23 rows ; ventrals 156- 



172 ; suhcaudals 68-64 4. pulcher, p. 539. 



*** Keels on the dorsal scales extending nearly to the 

 extremitj- ; scales in 21-23 rows ; ventrsis 157- 

 172 ; suhcaudals 40-74. 6. pietus, p. 540. 



/3. Loreal pit separated from the labials. 



* Keels on the dorsal scales much shorter than the 



scales; scales in 23 rows; ventrals 159-161; 

 suhcaudals 52-55 .... 5. microphtJiahmig, 



[p. 540. 



