580 VIPERID. 
Porthidium, Cope, Proc. Ac. Philad. 1871, p. 207. 
Atropophis, Peters, Ann. Mus. Genova, iii. 1871, p. 41. 
Rhinocerophis, Garman, Bull. Mus. Comp. Zool. viii. 1881, p, 85. 
Ophryacus, Cope, Bull, U.S. Nat. Mus. no. 32, 1887, p. 88. 
anatophis, Posada-Arango, Bull. Soc. Zool. France, 1889, p. 843. 
Upper surface of head covered with scales or small shields. Body 
cylindrical or compressed ; scales smooth or keeled, with or without 
apical pits. Tail moderate or short ; subcaudals single or in two 
rows. 
South-eastern Asia ; Central and South America. 
Synopsis of the Species. 
I, American species, with non-prehensile tail. 
A. Subcaudals all or greater part in two rows. 
1. Posterior subcaudals replaced by small scales; upper head- 
scales granular, smooth or obtusely keeled; supraocular 
shield narrow; scales tubercularly keeled, in 35 or 37 
rows ; ventrals 200-230; subcaudals 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. 
* Keels on the dorsal scales extending nearly to the 
extremity ; scales in 23-33 rows; ventrals 180- 
240 ; subcaudals 46-70. 2. lanceolatus, p. 535. 
** Keels on the dorsal scales much shorter than the 
scales. 
Scales in 25-29 rows; ventrals 161- 
216; subcaudals 47-73 .......... 3. atrow, p. 537. 
Scales in 21-23 rows; ventrals 156- 
172; subcaudals 58-64 .......... 4, pulcher, p. 539. 
*** Keels on the dorsal scales extending nearly to the 
extremity; scales in 21-23 rows; ventrals 157- 
172; subcaudals 40-74. 6. pictus, p. 540. 
B. Loreal pit separated from the labials. ° 
* Keels on the dorsal scales much shorter than the 
scales; scales in 23 rows; ventrals 159-161; 
subcaudals 52-55 .... 5. microphthalmus, 
[p. 540. 
