THEBA CANTIANA. 85 
HOoLocENE.—In Dorset, it is recorded from the tufaceous deposit at Blashenwell, 
Isle of Purbeck, by Mr. J. C. Mansel-Pleydell. 
In Kent, it is recorded from the post-Roman deposits, Buckland. Dover, by the 
Rev. R. A, Bullen ; and from alluvium in Erith Marshes by Mr. B. B. Woodward. 
In Surrey, it has been found in the upper two feet of deposit at Horseshoe 
Quarry, Reigate, by the Rev. R. A. Bullen and Mr. L. E. Adams. 
In Essex, it was found in shell-marl at Felstead, by Mr. J. French ; and also 
recorded from sand and shell-marl in the excavations for the reservoirs of the East 
London Waterworks, Walthamstow, by Messrs. Kennard and Woodward. 
In Herts., it was collected from the subsoil of a tumulus at Highly Hill, Ashwell, 
by Mr. H. G. Fordham. 
In Suffolk, it was recorded by the Geological Survey, from the railway cutting 
and bricky ard west of Sudbury. 
In York 8.E., it was found by Mr. Mortimer in a ‘‘barrow” of Bronze age, at 
Birdsall Brow, Drittield. 
Variation.—Though this species has so small a range of observed 
variation, it has been split up into a number of varieties and species, most 
of which differ from the type form in only a very slight degree. These 
named forms are about fifty in number, and their allocation has been 
attempted where any really definite character could be detected. 
Much confusion and uncertainty, however, exists, not only as to the 
status but as to the aftinities of many of the modifications, some believing 
certain forms are worthy of specific rank, while others refer them to the 
present species, or even to 7. cartustuna, as insignificant varieties. 
Though the variations in form are comparatively slight and infrequent, 
those of colour depend upon the presence, distribution, and intensity of 
the rufous-brown pigmentation, and of the presence or absence of the pale 
peripheral zone ; these traces of banding, which are probably vestigial and 
evidences of a former scheme of coloration are explained by the presence 
of the white supra-peripheral zone, only evident in the rufous-tinted shells, 
and which probably at one time formed the division between the upper and 
lower group of bands. 
The var. gaudefroyi, a native of St. Florent, Corsica, an insular region, 
practically at the extreme limit of the specific southern range, retains, 
according to the available description, the hispid periostracum in adult 
life, a peculiarity which may be explained by the Corsican form being an 
earlier or more primitive form of the species, which also probably ‘still 
inhabits more umbrageous surroundings than their continental relatives. 
The hispid epidermis in the more evolutionary active countries 1s now 
entirely restricted to the juvenile stage, and becomes totally lost before 
maturity. ‘This change is probably due to the adoption of a more open 
and exposed environment gradually diminishing the formerly existent 
epidermal outgrowths, and may be reminiscent of the remote period, when 
the country was more densely afforested than is now the case. 
In the Mediterranean region the general aspect of the shells as com- 
pared with North European specimens is to present a glossier and more 
finely striate surface, usually of a white or whitish colour with a stronger 
labial rib. 
The north European area of distribution, which includes England, North 
France, Holland, Belgium, and North Germany, produces a ruder and 
stronger race, which seems at the present day almost or completely severed 
from geographical continuity with the whiter and smoother Southern or 
Mediterranean group. 
