572 TIPEEIDJR. 



verse dark bars on each side opposite to the dorsal spots; head 

 without markings ; a brown nuchal spot, forked in front ; belly 

 yellowish, thickly variegated with blackish brown. 



Total length 200 millim. ; tail 22. 



Vera Cruz, Mexico. 



13. CROTALUS. 



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



p. 565 (1837) ; Dum. ^ Bibr. Erp. OSn. vii. p. 1453 (1854) ; Jan, 



Elenco sist. Ofid. p. 123 (1863). 

 Caudisona, Law. Syn. Rept. p. 92 (1768). 

 Crotalinus, Rajin. Amer. Monthly Mag. iii. 1818, p. 416. 

 Crotalus, Gray, Ann. Philos. 1825, p. 206 ; Fitzing. N. Class. Rept, 



p. 34 (1826) ; Wagl. Syst. Amph. p. 176 (1830) ; Gray, Zool. 



Miscell. p. 61 (1842), and Cat. Sn. p. 19 (1849) ; Cope, Proc. U.S. 



Nat. Mtis. xiv. 1892, p. 686 ; Stejneger, Rep. U.S. Nat. Mus. f. 



1893, p. 421 (1896). 

 Uropsopnus, Wagl. I. c. ; Gray, II. cc. pp. 51, 18. 

 Aploaspis, Cope, Proc. Ac. PMlad. 1866, p. 310. 

 .(Echmophrys, Coues, Wheeler^ Surv. W. 100th Merid. v. p. 609 



(1876). 



Head very distinct from neck, covered above with scales or small 

 shields ; eye moderate or small, with vertical pupil. Body cylin- 

 drical ; scales keeled, with apical pits ; veutrals rounded. Tail 

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

 rattle ; subcaudals all or greater part single. 



.America, from Southern Canada and British Columbia to Southern 

 Brazil and Northern Argentina. 



Synopsis of the Species. 



I. Supraocular shield not produced into a horn-like process. 



A. Eye separated from the labials by three to Ave rows of scales. 



1. Rostral as deep as broad or deeper than broad, in contact 

 with the nasal. 



a. Upper surface of snout covered with one pair of inter- 

 nasals and one pair of prsefrontals (with occasionally 

 one or two small scales between them) ; scales in 23-31 

 rows ; ventrals 160-199 1. terrificm, p. 573. 



h. Upper surface of snout with several small shields or 

 scales ; stales in 23-29 rows ; ventrals 165-197. 



a. Supraocular shields transversely striated, as broad as 

 or slightly narrower than the space between them. 



Two or three series of small shields between 

 the supraoculars, which are in contact 

 with four or five shields in addition to the 

 prae- and postoculars 2. scutulatus, p. 575. 



