572 VIPERIDZ. 
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, ae Linn. 8. N. i. p. 372 (1766) ; Schleg. Phys. Serp, ii. 
p- 555 ( 837) ; Dum. §& Bibr. Erp. Gén. vii. p. 1453 (1854) ; Jan, 
Elenco sist, Ona. p. 123 (1863). 
Caudisona, Laur. Syn. Reps p. 92 (1768). 
Crotalinus, Rafin. Amer. Monthly Mag. iii. 1818, p. 416. 
Crotalus, Gray, Ann. Philos, 1825, en 205 Fitzing. N. Class. Rept. 
34 if 1826); Wagl. Syst. Amp 176 qd my Gray, Zool. 
Wriscel 2. p. 51 (1842), and Cat. Sn. p. M0 (1849) ; Cope, Proc. U.S. 
Nat. Mus. xiv. 1892, p. 686; Stejneger, Rep. U.S. Nat. Mus. f. 
1893,  P- 421 (1895). 
pariah: us, Wagl. 1. c.; Gray, U. ce. pp. 51, 18. 
loaspis, Cope, Proc. Ac, Philad. 1866, 810. 
ate hmophrys, Coues, Wheeler’s Surv. W. 100th Merid. vy. p. 609 
(1875). 
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; ventrals 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 five 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 prefrontals (with occasionally 
one or two small scales between them); scales in 22-31 
rows; ventrals 160-199...... 1. terrificus, p, 573, 
b. Upper surface of snout with several small shields or 
scales ; scales 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 
pre-and postoculars .......ceeeeees . 2. scutulatus, p. 575. 
