PIT- VIPERS. 



247 



of shields on its lower surface. In all the Asiatic species there are two rows of 

 these subcaudal shields, and it is only in a few of the New World forms that they 

 are reduced to a single series. The number of longitudinal rows of scales on the 

 body is very variable in the different species, ranging from as few as thirteen to as 

 many as thirty -one. In Asia these snakes range from India to the South of China 

 and the Liu-Kiu Islands ; and while some species are terrestrial and normally 

 coloured, others are arboreal, and in the greenish tints assimilate to the colour of 

 their surroundings. The climbing tree-viper (Trimeresurus gramineus) belongs 

 to a group of four allied Indian and Burmese species, characterised by their 



RAT-TAILED PIT-VIPER (£ nat size). 



prehensile tails and the arrangement of the scales on the body in from thirteen 

 to twenty -three rows ; the figured species usually having twenty-one rows of scales, 

 while there are from seven to thirteen scales in a transverse series on the head 

 between the supraoculars; the temporal scales are smooth, and the shields on the lower 

 surface of the tail vary in number from fifty-three to seventy-five. Attaining a 

 length of 2 \ feet, this snake usually has the upper-parts bright green, although in 

 some specimens they may be yellowish, greyish, or purplish brown, while they may 

 or may not be marked with black, brown, or reddish spots. Generally there is a 

 light-coloured or reddish streak along the outer row of scales, and the end of the 

 tail is frequently red or yellow ; the under-parts being green, yellow, or whitish. 

 Ranging from Bengal to the Malayan region, this species is thoroughly arboreal in 



