, 
8 VITRINA PELLUCIDA. 
Geological History..-V. pellucida, though so fragile a species, has, 
nevertheless, been observed in a fossil state in our own and other countries. 
Prersrocenr.—Mr. Miller Christy records it from the alluvial deposits 
of the Cann Valley, North Essex, and Mr. A. 8. Kennard reports a speci- 
men of this species in the collection at the Museum of Practical Geology 
from the Forest-Bed series of the Lower Pleistocene formation. It has 
also been met with among the Pleistocene remains found in the Ightham 
fissure, Kent. 
In Germany it is mentioned by Sandberger as having been found in an 
imperfect state in the Pleistocene tufa at Cannstadt in Wurtemburg, and 
Weimar in Saxe- Weimar. 
In France, according to Mr. Blackmore, it has been found at the base of 
loess or Pleistocene fluvio-marine sand (sable aigre) at Menchecourt near 
Abbeville in the department of the Somme. 
Hotocene.—Mr. Kennard reports its occurrence in the pre-Roman 
peat deposits at Westbury-on-Severn, Gloucestershire; in a post-Roman 
hillwash at Ashford, Kent; a hillwash at Greenhithe, Kent; and in the 
comparatively modern deposit at East Farleigh near Maidstone. 
In Ireland it has been found by Mr. R. Welch in the deposits at Rosapenna, 
Donegal ; by Mr. J. G. Milne in those on the Warren, Achill Island, Co. 
Mayo; and by Messrs. Collier and Standen at Dog’s Bay, Connemara. 
Variation.— V. pellucidw varies comparatively little in size or shape. 
When full grown it may present a more flattened and oval outline (var. 
depressiuscula), ov may be more globose (var. dillwynii), but these modifi- 
cations are not striking. A var. perforata and a var. minor are described by 
Westerlund from Sweden, but no precise description of the latter is given. 
In colour, the shell varies from a crystalline transparency to a yellowish or 
greenish tint, the latter form being at one time described by Captain Brown 
as new, under the name of Helix virides. The occurrence of these colour 
variations has, however, never been systematically observed or recorded. 
A very beautiful specimen, found by Mr. L. E. Adams at Coleraine, Co. 
Derry, is spirally encircled with two broad milk-white bands, which extend 
from the apex to the aperture of the shell. 
Though I have never seen a British specimen of the true Vétrina major 
Fér. (V. draparnald: Cuvier), yet continental authors almost universally 
describe it as a British species, and allocate it with the Vitrina depressa 
and V. diuphana of Jeffreys, while Captain Brown in his “Land and 
Freshwater Conchology,” figures on pl. xx., f. 21, a specimen which 
appears referable to V. major, but of which he gives no particulars. 
‘hough the opinion of American authors would seem to be in favour 
of specific status being granted to Vitrina limpida, the eastern North 
American species, and to. V. alaskana, the inhabitant of the western part 
of that continent, as well as to V. angelica, of 
Greenland, and V. eaélis, of North-eastern Asia, esa 
yet all these forms are unquestionably very 
closely related, and are probably merely the Fie: 10 sz, weaseneatee es 
earlier offshoots from an identical stock, which — etlarged (fter Binney). 
do not yet display marked specific distinctions externally, but nevertheless 
according to the published descriptions do display a subtle gradation m 
the relative degree of shell deterioration such as might be logically 
expected from the geographical relationship of the areas they respectively 
occupy, while the internal structure of the various forms has not as yet 
been properly examined or compared. 
