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 (jt 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 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. 
Banging from Bengal to the Malayan region, this species is thoroughly arboreal in 
