The first genus is the Crotalus, or rattlesnake proper; the second is the Caudisona, or ground-rattlesnake; the third is the Ancistrodon, or moccasin, one of the species of which is a water-snake; and the fourth is the Elaps, or harlequin snake.    From Wordnik.com.  [Anomalies and Curiosities of Medicine] Reference