240 BRITISH SERPENTS. 
difference shown in the average size of our adders in 
different localities, and this is a question that awaits 
elucidation. The fact that the sinall red viper occurs 
in fifteen counties where the ordinary adder is 
also found, thoueh the two differ greatly in size as 
well as in appearance, is very interesting. But the 
adder itself also exhibits great variation in size. Thus 
in Sussex it scems to attain its maximum size at 20 
inches, while in Herefordshire the average is 24 
inches, and specimens of 26 inches are not unusually 
taken; and in Scotland 24 inches is a very usual 
measurement. In Devonshire the size varies greatly 
in different parts, and in this case the small measure- 
ments may be those of the small red viper, the large 
one the ordinary adder, as both varieties are found in 
the county. 
In the Isle of Man, as in Iveland, there are, I am 
informed, no snakes at all; and the same local immun- 
ity is reported from Guernsey and Sark. 
Finally, we may sum up the most prominent 
features of the county and local records, taking the 
areas In groups, as divided in the biological chart 
referred to above. 
I. Peninsula Province. 
Vipera berus.—Vhere is no doubt that the adder 
iS more common than the rine snake in Cornwall; 
but opinions differ regarding Devon, no doubt because 
the two snakes have their own habitats. In the latter 
