459 
Table lands. The reverse might certainly have been expected. But 
then the question arises, Are these two, H. fulvius and LE. corallinus, 
really distinct species? The basis of the distinction seems to be laid 
entirely on the coloration, as no structural differences are traceable. 
It is true that the two, as I have given them above, represent great di- 
versity in the number of the rings; but this inequality, being so notice- 
able in specimens that are certainly of the same species, seems to re- 
solve itself into merely one of amount. The manner of arrangement is 
precisely the same in both, the series of rings being equidistant in both 
the species under consideration. If, then, we reject the number of 
rings as an insufficient ground for specific distinction, the other dif- 
ferences, such as the yellow bands and the intermediate black mark- 
ings, can hardly be considered as such when no two specimens are 
exactly alike. The inequality existing in the number of the ventral 
plates and the proportion they bear to the caudal is such, that, if 
any one of the five specimens I have described be entitled to bear a 
specific appellation, so are they all. 
Besides the great variation shown by my specimens, an examina- 
tion of the series in the British Museum at once indicates that the 
great difference between extreme varieties can be filled in by an almost 
consecutive series of minor distinctions. Nor can these varieties be 
classed under the head of local varieties, and thus substantiate a title 
to specific distinction. In the present instance we find three, all of 
which bear separate names, inhabiting the same country. The de- 
duction that Hlaps corallinus and E. Sulvius, and all the varieties 
which have been collected under each of these heads, belong in 
reality to one highly variable species, seems inevitable. 
THAMNOCENCHRIS, n. g. (CROTALIDZ.) 
A pit on each side of the face. Posterior part of the body and 
tail much compressed, the latter ending in a horny spine. Sub- 
caudals one-rowed. Tail prehensile. Head angular, anteriorly 
covered with irregular shields, and having small keeled scales poste- 
riorly. No small scales between the superciliary and the orbit. The 
second upper labial forms the anterior part of the facial pit. 
THAMNOCENCHRIS AURIFER, sp.n. (Pl. XXXII. fig. 1.) 
Scales keeled in nineteen rows. Nine upper labial shields. Small 
shields between the fourth labial and the orbit. Green, with a dorsal 
series of orange spots edged with black. A pines band from the 
orbit to the side of the occiput. 
Hab. Coban, Vera Paz. 
This new form is distinguished from Teleuraspis (Cope) by its 
peculiarly compressed body and tail, the latter being coiled as in 
some of the Boide, clearly indicating a habit of living in trees. It 
also differs from Botriechis*, Peters, in having very large shields 
instead of very small scale-like ones on the upper surface of the 
snout. Nor does Prof. Peters mention in his description the pecu- 
* Monatsb. Akad. Wiss. Berlin, 1859, p. 278. 
