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 small red viper occurs 

 in fifteen counties where the ordinary adder is 

 also found, though 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 seems 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 Ireland, 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. 



Vipcra herns. — There is no doubt that the adder 

 is more common than the ring snake in Cornwall; 

 but opinions differ regarding Devon, no doubt because 

 the two snakes have their own habitats. In the latter 



