47. SISTRURUS 7 905 
salt solution may be tried. Resort may be had to artificial 
respiration when respiratory paralysis precedes failure of 
the circulation. 
Genus 47. Sistrurus 
Crotalus Furminc, Philos. Zool., Vol. II, 1822, p. 294 (type, C. miliaris) 
(not of Linn.). 
Crotalophorus Gray, Ann. Philos., 1825, p. 205 (not of Houttuyn). 
Caudisona Firzincer, Neue Class. Rept., 1826, p. 34 (type, C. miliarius) 
(not of Laurenti). 
Sistrurus Garman, Mem. Compr. Zool., Cambr., Vol. VIII, No. 3, 
1883, p. I10 (type, C. miliarius). 
The head is broad and low, with flattened top, and is very 
distinct from the neck. Its upper surface is covered with 
nine large plates, the internasals, prefrontals, frontal, supra- 
oculars, and parietals. The anal plate and most of the 
urosteges are undivided. The tail is short and ends in a 
horny rattle or button. The scales are keeled. 
The snakes of this genus differ from the rattlesnakes of 
the genus Crotalus in having the head covered above with 
large plates instead of small scales. The few species known 
are all of small size, and therefore, correspondingly less 
dangerous than the larger rattlesnakes. One kind has been 
found in southern Arizona. 
207. Sistrurus catenatus edwardsii (Baird & Girard) 
Epwarps MassasauGA 
Crotalophorus edwardsii Bairpv & Girarp, Cat. N. Amer. Rept., Pt. 1, 
Serpents, 1853, p. 15 (type locality, Tamaulipas, Mexico); Dum- 
ERIL et Brsron, Erpétol. Génér., Vol. VII, 1854, p. 1483; Barro, 
U. S. Mex. Bound. Surv., Vol. II, Rept., 1859, p. 15, pl. V, fig. 1; 
Barro, Rep. Pac. R. R. Surv., Vol. X, Rept., 1859, pl. XXYV, fig. 
10; Duces, La Naturaleza, Vol. IV, 1879, p. 27. 
Crotalus edwardsii Corr, Mitch. Res., 1861, p. 125; Cougs, Surv. W. 
tooth Merid., Vol. V, 1875, p. 610. 
