12. SISTKTJETTS. 569 



imbricate, large, shield-like and smooth or feebly keeled on the 

 snout and vertex ; an enlarged frontal, separated from the large 

 supraocular by a series of two or three smaller shields ; intern asals 

 small ; two postoculars and a subocular, separated from the labials 

 by one series of scales ; temporal scales keeled ; 9 or 10 upper 

 labials, second forming the anterior border of the loreal pit. Scales 

 rather strongly keeled, in 19 rows. Ventrals 154-158 ; anal entire ; 

 subcaudals 63-61, single. Tail prehensile. Green above, with 

 more or less distinct, scattered yellow spots ; a more or less distinct 

 black streak on the temple ; greenish yellow beneath. 



Total length 825 millim. ; tail 145. 



Guatemala. 



a. 2 (V- 154 ; C. 53). Cohan, \era Paz. O. Salvin, Esq. [0.]. 



(Type.) 

 i. d (V. 158; 0.61). Cohan. 0. Salvin, Esq. [C.]. 



12. SISTRUEUS. 



Crotalus, part., Linn. S. N. i. p. 372 (1766) ; Schleg. Phys. Serp. ii. 



p. 565 (1837) ; Bum. ^ Bibr. Erp. GS-ti. vii. p. 1453 (1854) ; Jan, 



Menco mt. Ofid. p. 123 (1863). 

 Crotalophorus {non Soutt.), Gray, Ann. Philo». 1825, p. 205, and 



Cat. Sn. p. 17 (1849) ; Cope, Proc. U.S. Nat. Mus. xiv. 1892, 



p. 684. 

 Caudisona {non Laur.), Fitzing. N. Class. JRept. p. 34 (1826) ; Wayl. 



Syst. Amph. p. 176 (1880) ; Gray, Zool. MisceU. p. 51 (1842). 

 Sistrurus, Garm. N. Am. Rept. p. 110 (1883), and Science, xix. 



1892, p. 290 ; Stejneger, Pep. U.S. Nat. Mus. f. 1893, p. 410 



(1895) ; W. E. Taylor, Am. Nat. 1895, p. 283. 



Head very distinct from neck, covered above with nine large 

 symmetrical shields ; eye moderate or small, with vertical pupil. 

 Body cylindrical ; scales keeled, with apical pits ; ventrals rounded. 

 Tail short, ending in a segmented, horny, sound-producing apparatus 

 or rattle ; subcaudals all or greater part single. 



North America East of the Eocky Mountains ; Mexico. 



Synopsis of the Species. 



Eostral as deep as broad or deeper than broad ; 



loreal separa^^ing the upper praeocular from 



the posterior nasal ; canthus rostralis sharp. 1. miliarius, p. 569. 

 Eostral as deep as broad or deeper than broad ; 



upper prseocular in contact with the posterior 



nasal ; canthus rostralis sharp 2. catenatus, p. 570. 



Eostral broader than deep ; loreal separating 



the upper prseocular from the posterior 



nasal ; canthus rostralis obtuse 3. ravus, p. 571. 



1. Sistrurus miliarius. 



Crotalus miliarius, Linn. S. N. i. p. 372 (1766) ; Baud. Pept. v. 

 p. 328 (1803); Say, Amer.Journ. So. i. 1819, p. 263 ; Harl. Journ. 

 Ac. Philad. v. 1827, p. 371, and Med. Phys. Pes. p. 134 (1835) 



