THEBA CANTIANA. 93 
Geographical Distribution.— Theba cantiana is apparently quite 
unknown in Scotland, Ireland, and on the western coast of England, as a 
result of natural diffusion. 
In England its range is exceedingly compact, and embraces every 
county and vice-county on the eastern and southern coasts from South 
Northumberland to South Devon, also occupying the neighbouring inland 
counties, without a single detached outher throughout its whole range. 
: yn APTS 
Fic. 139.—Geographical Distribution of Theba cantiana (Mont.). 
Probable Range PM Recorded Distribution 
Although many attempts have been made with varying success to 
establish this species in localities where it was not previously known to 
exist, both within and beyond its known range, its natural distribution 
has not been very materially interfered with in England. 
The attempts to found local colonies by Prof. Boycott in Herefordshire, 
and by Mr. J. C. Blackshaw near Wolverhampton, would seem to have 
been more or less successful, while many others, like Mr. Swanton’s effort 
to establish a colony in Somerset, were failures. 
It was also introduced into Cumberland, where it was not previously 
known to exist, by Capt. Farrer, in Aug. 1894, who liberated a number of 
specimens near Bassenthwaite, which largely increased in numbers the 
following year and seemed likely to spread. 
Its presence along the banks of the Tees and Tyne and elsewhere in 
Northumberland and Durham has been very generally attributed to its 
inadvertent introduction with ballast by the “colliers” trading from the 
ports on those rivers, but no evidence has been adduced, beyond the shells 
being found plentifully on the ballast-hills of the river-banks. 
In Wales it is known from Glamorganshire, where it is locally common. 
In Scotland this species is naturally quite unknown, but specimens 
from England were introduced in 1888 into his garden at Brora, Kast 
Sutherland, by Mr. W. Baillie, which have apparently prospered, as in 
1895 Mr. Baillie reported that owing to their increasing abundance he had 
been compelled to remove hundreds of specimens to other places, 
