While there are three genera of vipers in America, two of them are so closely related, and present characteristics that are so similar that the ordinary observer would regard them as being identical, and inasmuch as the character of their poison seems in every way similar, for practical purposes it would seem desirable to include them under one head; in both genera, the species have rattles on the tips of their tails, the more common being the ordinary rattlesnakes (genus _Crotalus_), of which there are twelve species in the United States, and the ground-rattlesnakes (genus _Sistrurus_), of which there are two species. Closely related to the rattlesnakes are the true moccasins, of which there are two species, one being the cotton-mouth or water-moccasin (_Ancistrodon piscivorus_), and the other the highland moccasin, pilot-snake or copper-head, (_Ancistrodon contortrix_). The two species of poisonous colubrine serpents already referred to are known respectively as the _Elaps fulvius_, and the _Elaps euryxanthus_, both of which occur in the southern portions of the United States. These snakes are fortunately of a very mild disposition, and rarely attempt to bite, even when handled. That their poison is exceedingly deadly is attested by the fact that out of eight instances where it was known that persons were bitten by them, six died, and they should, therefore, be looked upon as among the most deadly of North American serpents. Mention should be made of the fact that there are at least six harmless reptiles that resemble the coral-snakes very closely, and as a consequence of the former being mistaken for the latter, the assertion has been frequently made by the ignorant that our elapine serpents are harmless. A short description of the really deadly reptiles encountered in this country that would enable even the novice to distinguish them from those that are harmless would seem not inappropriate here, for where a person is bitten by a snake it becomes at once a matter of vital importance to determine, if possible, its true character. Most non-venomous serpents will viciously bite when cornered, and while they may produce slight wounds, with a small amount of bleeding, such injuries are entirely devoid of danger, and need occasion no fear on the part of the victim. There now follows a brief description of our venomous snakes, by means of which it will be easy for any one to distinguish them from their innocent relatives.