384 OPHIDIA. 



Synopsis of the Indian Genera. 



IJ^pper side of the head covered with small scales, only the foremost part of the 



snout being shielded Trimeresvrus, p. 384. 



Upper side of the head with large shield-like scales. Scales very large .... Peltopelor, p. 390. 



Head entirely shielded above ; scales smooth Calloselasma,^. ZQ\. 



Head entirely shielded above ; scales keeled Halys, p. 393. 



Snout covered with small irregular shields above, the shields of the remainder of 



the head being normal Hypnale, p. 394. 



TRIMERESURUS*. 



Trimeresurus, sp., Lacep. Ann. Mus. 1804, iv. p. 196. 



Head triangular, covered above with small scales, except the foremost 

 part of the snout and the supraclliary region, which generally are shielded ; 

 body with more or less distinctly keeled scales, in from seventeen to twenty- 

 seven series. Body and tail of moderate length, prehensile. Subcaudals 

 two-rowed. 



The Trimeresures are Tree-snakes, as is indicated by their prehensile tail and by their green 

 or varied coloration. In general they are sluggish, not attempting to move out of the vpay, 

 and as they very closely resemble the branch on which they rest, they are frequently 

 not perceived until they prepare to dart, vibrating the tail and uttering a faint hissing 

 sound, or until they have bitten the disturber of their rest. Accidents caused by these 

 snakes, therefore, are not of uncommon occurrence, and it is a fortunate circumstance that 

 comparatively but few examples attain to a size of more than 2 feet, so that the consequences 

 of their bite are less to be dreaded than of other poisonous snakes. Indeed, numerous cases 

 are on record which show that the symptoms indicating a general effect on the system were 

 of short duration, extending only over the space of from two to forty-eight hours, and con- 

 tined to vomiting, nausea, and fever. After the pain and swelling of the bitten member or 

 spot have subsided, the vicinity round the wound becomes discoloured, mortifies, and is finally 

 thrown off as a black, circular slough, after which health is speedily restored. The bite of 

 larger specimens, from 2 to 3 feet long, is more dangerous, and has occasionally proved fatal : 

 so that the greatest care should always be observed in the immediate treatment of the patient. 



* We include in this genus not only the species of Trimesuriis, Gray, but also those of Farias, Gray, 

 and of Meg<era, "Wagl. ; the two latter genera having the scales keeled, and not smooth, as has been 

 stated by several herpctologists. The keels are faint in some specimens, and sometimes become almost 

 invisible when the specimens have been badly preserved, or when the epidermis has been lost. The frontal 

 shields, which are well developed in T. trigonocephalus, are present, but smaller, in the other species. A 

 division of the supraorbital plate, which is constant in one species, is occasionally found in species which 

 usually have it undivided. Osteological characters, like the greater or less width of the skull, do not 

 appear to me to be of greater value than those external ones which I have mentioned. 



