832 EEPTILIA. 



As in T. monticola, the sub-caudals of this species have some of their number 

 entire. 



This species does not appear to be so arboreal in its habits as some of the others. 

 Stoliczka obtained it on the limestone hills near Moulmein, and Theobald records 

 that he found a single specimen in the caves near the same locality. The larger 

 of the two specimens I procured, I encountered on the limestone rocks, below the 

 Yethaycoo pagoda, in the second defile of the Irawady, lying coiled up on the 

 ground, ready to strike. 



Trimeresuetjs monticola, Giinther. Plate LXXVI, figs. 4 & 5. 



Farias maculata, Gray, Ann. and Mag. Nat. Hist., vol. xii, 1853, p. 39^. 



Trimeresurus monticola, Gnnther, Rept. Brit. Ind., 1864, p. 388, pi. xxiv, B. j Theobald, Journ. 

 As. Soc, Bengal, vol. xxxvii, 1868, ex No., p. 76 ; id., Descr. Cat. Rept., Brit. Ind., 

 1876, p. 220; Anderson, Proc. Zool. Soc, 1871, p. 194 j Fayrer, Thanat. of India, 1872, 



pi. XV. 



In the valley of Hotha, this species is not at all uncommon, and I obtained 

 four examples of different ages. Two of these specimens, unlike the types of 

 the species and the other examples from Western Yunnan, have the second labial 

 distinct from the plate in front of the facial pit. In the T. mutabilis, Stoliczka, 

 the second upper labial may either form the front of the facial pit, or it may occa- 

 sionally be divided in two. A similar variation occurs in the Trimeresurus referred 

 by Stoliczka^ to T. andersoni. This variation, however, as far as my observations go, 

 would appear to be a rare occurrence, because in the extensive series of Trimeresuri 

 in the British Museum, I have failed to detect a single instance in which the second 

 labial when it forms the front of the facial pit is completely divided, or an example 

 in which the second labial, when it does not enter into the facial pit, unites 

 with the shield that does. In one individual, however, of T. anamallensis, 

 the second labial shows a tendency to division on one side. The occasional divi- 

 sion, however, of the second labial into a facial pit-shield in T. monticola and 

 in T. mutaUUs introduces another element of difficulty in determining what 

 are really reliable specific characters, so far as the Trimeresuri are concerned ; 

 for those characters, which, in other snakes, are generally guides to the species 

 by reason of their stability, are obscured in the Trimeresuri by their varia- 

 bility. 



The scales in these Yunnan specimens which are all from one locality, viz., the 

 outskirts of the small town of Hotha, vary from 23 to 25, but in Himalayan 

 examples of the species there are occasionally 26 rows of scales. The ventrals in 

 the two specimens in which the second labial does not enter into the facial pit 

 number 151 and 156 each, with 41 and 57 sub-caudals respectively with the anal 



1 Journ. As. Soc, 1871, p. 443. 



