INTRODUCTION. sy 
shells by persons of the highest integrity, with the assurance that they 
came from such and such a place in the British Isles. I am sure the 
majority of collectors have undergone similar experiences. 
In order that a collection may be of any value, it should be, like 
Ceesar’s wife, ‘‘ above suspicion.” 
NUMBER OF BRITISH SPECIES AND VARIETIES. 
Though the entire list of British land and freshwater species is 
limited to 127, there are numerous varieties ; so that while a fair col- 
lection is within the reach of most people—often within the range of 
a single county —an absolutely perfect collection is never arrived at. 
As an example of what a single district with a radius of five miles 
from a head-quarters may produce, I instance Stafford with 32 aquatic, 
38 terrestrial species ; total 70. This being a red sandstone district is 
not particularly favourable for land shells. Other districts I have 
worked in the South and North of England are much richer, but I 
take Stafford as an average field for research. 
VARIETIES. 
For the vexed question of varieties there is not room to enter here. 
Suffice it to say that the beginner need not trouble himself about them, 
but will be able to distinguish them by degrees. |The present formi- 
dable array is that authorized by the Conchological Society. 
It should be noted that a single varietal name will not always fully 
describe a given specimen; in such cases the names may be combined 
thus :—Helix rotundata var. turtont-albida; H. memoralis var. 
rubella-minor-albolabiata, 123(45). 
FOREIGN SHELLS RECENTLY INTRODUCED INTO THE 
; BRITISH ISLES. 
Within the last few years several mollusks have been noticed for 
the first time in the British Isles. P/lanorbizs dilatatus, which came 
from America about 1864 in cotton bales, has made itself at home 
near Manchester and Burnley, and has been admitted to rank with 
C 
