198 BRITISH SERPENTS. 
had stated. Of course this was not sufficient basis 
for a final conclusion, but it was sufficient to show 
that I was dealing with a locality in which the adder 
was the most common serpent found, and that it did 
attain a very large size here. The sixth adder in the 
list was a very young male, and evidently not mature. 
The female of 284 inches, taken within a few hundred 
yards of my own doors, is the largest adder I have 
ever captured, and one of the largest I can obtain 
authentic measurements of in any district. Since 
1897 I have measured a large number of adders 
taken in this part of the Monnow Valley, and of 
the whole series (over a hundred specimens) I find 
that— 
The adult male averages 24 inches. 
" female " 254 " 
If these figures are compared with the averages given 
under the heads of the various counties, it will be 
found that the adder in the Monnow Valley attains its 
maximum length for these isles. 
Are there, then, no other snakes in this valley but 
adders? The gamekeepers, farmers, and others all 
told me that no other species was to be found, which 
of course meant that they had seen no other kind, and 
for two and a half years I never saw any other serpent 
here but the adder. Then on the 26th September 
1898 I saw the small specimen of Tropidonotus natrir 
referred to in the chapter on that species, where the 
