_Scytale cupreus_, Copper-head, &c. of Mr. Rafinesque. I have always considered the Copper-head to be no other than the _Cenchris mockeson_ of authors, and _Boa contortrix of Linn._ v. Latr. Lacep. Shaw, Daudin, &c. _Agkistrodon mokasen_ of Beauvois; which opinion is not a little corroborated by an actual comparison of one of these animals in Peale's Museum, with the descriptions of the authors above mentioned. It may be objected to me, that the _mockeson_ of those naturalists is a _Cenchris_, and not a _Scytale_, therefore generically distinguished from the Copper-head; but on the other hand, we know that the genus _Cenchris_ does not exist in nature, that the individual upon which it was founded, was either a fortuitous variety, or that the illustrious naturalist was deceived by the desiccation of his specimen, giving to the basal caudal plates a bifid aspect. That the former was the case I analogically infer, from having seen, in the collection of the Academy of Natural Sciences, a _Coluber heterodon_, of which the fifth and sixth pairs of caudal scales were entire, and not as usual bifid. An additional corroboration of the truth of this inference is derived from the circumstance of the _Scytale_ of Peale's Museum, having the ten or eleven apical caudal plates bifid, precisely as in the genus _Acanthophis_, to which it seems closely affianced, and to which it would be referred if this character was a permanent one. In every other character this specimen coincides with the _S. mockeson_ of authors, and in every necessary respect with the _S. cupreus_ of Mr. R. with the sole exception of the calcarate termination of the tail. This caudal horn seems to approximate Mr. R's. animal to the _S. piscivorus_ or true horn-snake, about which the credulous have so absurdly alarmed themselves, and which was arranged with the _Crotali_ by Lacepede, in consequence of having a horn on the tail an inch long. We find sometimes a small indurated tip to the tail of _Coluber melanoleucus_,[33] at least upon some full grown specimens, formed by the elongation and appression of the terminal scales; a larger one on that of the European viper, and of the _Acanthophis cerastes_, and _Brownii_. Mr. Peale's specimen certainly has not the horn, but it has at the termination of the tail a scale somewhat longer and more indurated than the others, the individual had not attained his full growth. If then this species (and some others) is subject to vary in the form of its caudal plates, from which the generic characters are in part estimated, may it not also vary in the armature of the tail, which at most can only be considered as specific. The Copper-belly is a very distinct species. If the _S. cupreus_ is, notwithstanding the above observations, considered a distinct species, it would gratify those who cultivate natural history, to have some good discriminative characters of it.