13. oROTALirs. 673 



Three to ten series of scales between the 

 supraoculars, which are in contact with 

 six to eleven scales in addition to the prse- 

 and postoculars 3. conjluentus, p. 57t). 



(i. Supraocular shields smooth, much narrower than the 

 space between them. 



Two pairs of intemasals ; rostral deeper than 



broad 4. durissus, p. 578. 



One pair of intemasals ; jrostral, as deep as 



broad 5. Jiorridus, p. 578. 



2. Eostral broader than deep, in contact with the nasal ; 



scales in 23 or 25 rows; ventrals 166-181. 



6. tigris, p. 580. 



3. Eostral broader than deep, separated from the nasal by 



scales; scales in 25 rows; ventrals 178-198. 



7. mitchelli, p. 580. 



B. Eye separated from the labials by one or two rows of scales. 



1. Upper prseocular normal, separated from the nasal by a 



loreal ; rostral as deep as broad. 



Two intemasals ; scales in 21-25 rows ; 



ventrals 142-184 8. triseriatus, p. 581. 



Pour intemasals ; scales in 27-30 rows ; 



ventrals 123-151 9. polystictus, p. 582. 



2. Upper prseocular divided into two by a vertical suture ; 



rostral broader than deep ; scales in 21-23 rows ; ventrals 

 153-169 10. Upidus, p. 582. 



II. Supraocular produced into a horn-like process ; scales in 21 or 

 23 rows ; ventrals 146 11. cerastes, p. 583. 



1. Crotalus terriflcus. 



Seba, Thes. ii. pi. xcv. figs. 1 & 2, & pi. xovi. fig. 1 (1735). 



? Crotalus dryinas, Linn. S. N. i. p. 872 (1766). 



Caudisona terrifica, Laur. Syn. jRept. p. 93 (1768) ; Cojpt, Proc. Ac. 



Philad. 1866, p. 308. 

 ? Caudisona dryinas, Laur. I. c. p. 94. 

 Caudisona orien talis, Laur. I. c. 

 Crotalus boiquira, part., LacSp. Serp. ii. pp. 130, 190 (1789). 



durissus, var., Shaw, Zool. iii. pi. xc. (1802). 



horridus (non L.), Latr. Sept. iii. p. 186 (1802) ; Baud. Sept. 



V. p. 311, pi. Ixix. fig. 1 (1803) ; Sari. Proc. Ac. Philad. v. 1827, 



p. 370; Wied, Ahbild. Nat. Bras. (1827); Schleg. Phys. Serp. ii. 



p. 661, pi. XX. figs. 12-14 (1837) ; Bum. Sf hibr. vii. p. 1472, 



pi. Ixxxiv. b. fig. 2 (1854) ; Hensel, Arch. f. Nat. 1868, p. 338 ; 



Jan, Icon. Gen. 46, pl. iii. figs. 1 & 2 (1874) ; Peracca, Boll. Mus. 



Torino, x. no. 195, 1895, p. 22. 

 cascavella, Wagl. in Spiv, Serp. Bras. p. 61, pl. xxiv. 



(1824). 



