94 BRIETISIE SERPENTS, 
with the size of the adder. “Its length is contained 
in the total from 5) to 7% times in .the males, 8 
to 9? times in the females.”! The tail in the males 
is not so sharply defined from the body as in females, 
the whole adder tapering to a point without showing 
distinetly where the 
sy 
tail becins. In females 
the tail is much more 
obviously an appendage, 
being sharply defined, 
not so thick, and coming 
more abruptly to a 
point. The extra thick- 
ness of the male tail 
is due to the presence 
in the anterior portion 
of it of the reproduc- 
tory organs of that sex. 
A side view of the tails 
Fic, 21.— Mare Fig. 22.— FEMALE 
Tat (3 in.) of the two sexes at once 
Tarn (24 in.) 
brings the differences in 
the tails into prominence. Diagrammatically they 
are shown above, 
Number of shields—The male tail being the longer, 
it is to be expected that the sub-caudal shields in 
that sex are more numerous than in the female. 
“The number (counting each pair as one, and not 
reckoning the terminal, conical, or spine-like shield) 
| Boulenger, Zoolovist, March 1892. 
