CROTALUS.-Linnseiis.Genus Crotalus.-Characters.Head very large, triangular, rounded in front and covered above, with small plates in front and with scales on the vertex and occiput; a deep pit between the eye and nostril; upper jaw armed with a movable fang on each side; body thick, robust; tail short, thick, and terminating in rattles, which are corneous productions of the epidermis; belly and under surface of tail covered with plates.