520 TIPEBIB^. 



from the labials by suboculars ; scales 

 in 23 (rarely 25) rows; ventrals 



135-141 ; subcaudals 52-64 2. bilineatus, p. 521, 



A loreal, usually separating the upper 

 prseocular from the posterior nasal ; 

 eye separated from the labials by 

 suboculars ; scales in 23 (rarely 25) 

 rows ; ventrals 145-155 ; subcaudals 

 31-52 3. contortria;, p. 522. 



6. Snout ending in a pointed appendage ; scales in 21 rows ; 

 ventrals 162-166 ; subcaudals 58-60. 



4. acutus, p. 524. 



2. Subcaudals all paired ; loreal pit separated from the labials ; 

 ventrals 137-174 ; subcaudals 31-55. 



a. Posterior labials distinct from the temporals. 



Snout slightly turned up at the end ; 



scales in 23 rows 5. halys, p. 524, 



Snout not turned up ; scales in 23 



(rarely 21) rows 6. intermeclius, p. 525. 



Snout not turned up ; scales in 21 



(rarely 23) rows 7. hlomhoffii, p. 525. 



h. Posterior labials fused with the temporals ; snout slightly 

 turned up ; scales in 21 (rarely 23) rows. 



8. himalayanus, p. 526. 



B. Scales smooth, in 21 rows ; ventrals 138-157 ; subcaudals 

 34-54 pairs 9. rhodostoma, p. 627. 



II. Scales in 17 rows, more or less distinctly keeled ; snout 

 strongly turned up, covered above with small shields ; ventrals 

 126-155 ; subcaudals 28-45 pairs . 10. hypnale, p. 528. 



1. Ancistrodon piscivorus, 



Crotalus piscivorus, part., Lacep. Serp. ii. pp. ISO, 424 (1789). 

 Scytale piseivora, part, Latr. Hept. iii. p. 163 (1802) ; Baud. Bept. 



V. p. 344 (1802). 

 Coluber aquaticus, part., Hhaw, Zool. iii. p. 425 (1802). 

 Acontias leucostoma, Troost, Ann. Lye. }f. T. iii. 1836, p. 176. 

 Trigonocephalus cenchris, part., Schley. Phys. Serp. ii. p. 553 (1837). 

 piscivorus, Holbr. N. Am. Herp. ii. p. 63, pi. xiii. (1838), 



and 2nd ed. iii. p. 33, pi. vii. (1842) ; Bum. §• Bibr. vii. p. 1491, 



pi. Ixxxii. 6. fig. 2 (1854) ; Jan, Icon. Gin. 46, pi. iv. (1874) ; 



Bovourt, Miss. 8c. Mex., Bept. pi. xxvii. (1882). 

 Cenchris piscivorus, Ch-ay, Zool. Miscell. p. 51 (1842), and Cat. p. 16 



(1842). 

 Toxicophis piscivorus, Baird ^ Gir. Cat. N. Am. Bept. p. 19 (1853), 



and Bep. Explor. Surv. B. B. x. Bept. pi. xxv. fig. 13 (1859). 

 pugnax, Baird Sr Gir. II. cc. p. 20, fig. 14, and Bep. U.S. Mex. 



Bovnd. Surv. ii., x. Bept. p. 16, pi. vi. (1859), 



