Say on Herpetology. 257 
Latr. Lacep. Shaw, Daudin, &c. Agkistrodon mokasen Beau- 
_ ¥ois; 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 object- 
ed to me, that the mockeson of those naturalists is a Cenchris, and 
not a Scytale, therefore generically distinguished from the Cop- 
per-head; but on the other hand, we know that the genus Cen- 
chris does not exist in nature, that the individual upon which it - 
was founded, was either a fortuitous variety, or that the illustri- 
ous naturalist was déceived by the desiccation of his specimen, 
giving to the basal caudal plates a bifid aspect. That the form- 
er was the case I analogically infer, from having seen, in the 
collection of the Academy of Natural Sciences, a Coluber hetero- 
nm, of which the fifth and sixth pairs of caudal scales were en- 
tire, and not as usual bifid. An additional corroboration of the 
truth of this inferencé is derived from the circumstance of the 
Scytale of Peale’s Museum having the ten or eleven apicial cau- 
dal 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 
is specimen coincides with the S. mockeson of authors, and in 
evel necessary respect with the S. cupreus of Mr. R. with the 
| le exception of the calcarate termination of the tail. This 
udal horn seems to approximate Mr. R’s animal to the S. pis- 
wus or true horn-snake, about which the credulous have so 
ns alarmed themselves, and which was arranged with the 
rotali by Lacepede, in consequence of having a horn on the 
We find sometimes a small indurated tip to 
tinal Scales; a larger one on that of the European viper, and 
m This large species I understand has been mistaken by a writer on Natural 
History * Boa constrictor: this is mentioned te show how remotely it iz ~ 
Possible to diverge from accuracy in this scienee. a 
You. 1....No. 3. 
