12 Description of Five New British Species of Shells. 
3. Crassina ovata. 
Shell thick, strong, and sub-compressed, with broad elevated 
parallel transverse ridges, which become nearly obsolete as they 
approach the base of the shell; it has a strong central tooth, and. 
a very small oblique tooth in the right valve ; left valve with two 
strong central teeth ; umbo reclined; under which the cordiform 
depression is lanceolate, deep, and large. Inside blueish white, 
with a broad and plain margin; the muscular impressions very 
large and deep. Colour of the epidermis dark-burnt umber. 
This species has much the appearance of the Crassina Scotiea, 
but differs from it in being more ovate, much stronger, and in the 
muscular impressions being nearly double the size, and in the cor- 
diform depression being also much longer and deeper. 
The Crassina ovata was discovered near Helensburgh, mouth 
af the Clyde, by Henry Witham, Esq. where it appears to be not 
uncommon. The specimen from which my figure was drawn, is 
in the cabinet of James Gerard, Esq. 
; si I. Fig. 8. Fig. 9. a section showing the thickness of the 
shell. 
4. Cyclostoma marmorea. 
Shell with five ventricose and deeply divided volutions, tapering 
suddenly to an obtuse apex. The aperture is quite orbicular ; the 
inner lip slightly reflected on the base of the columella, behind 
which is a deep umbilicus. This shell is smooth, glossy,.and of a4 
pale ash colour, covered with zigzag markings of a reddish chesnut 
brown, which form four spiral fascize on the lower volution, and 
gradually become obsolete in the upper portion of the spire. Plate 
I. Fig. 10. and 11. | 
I noticed this elegant shell in the cabinet of Mr Gerard, asso- 
ciated with some British specimens of the Cyclostoma elegans, te 
which it is closely allied, but may at once be distinguished from 
that shell, being totally devoid of striz, which in the elegans are 
very strong and conspicuous. 
5. Helix vitrea. 
Shell much depressed, thin, and of a greenish white ; volutions 
six ; aperture large, semi-lunate, and enveloping the body whirl 
with a deep but small umbilicus ; size an eighth and a sixteenth 
of aninch. It has somewhat the appearance of the young of the 
Helix nitens, but may at once be distinguished, from having a 
greater number of volutions, and being thicker, with the volutions 
mere depressed on the apex. | 
: ee 12. size of nature. Fig. 13. and 14. top and bottom mag- 
nified. 
Two specimens of this shell were found by Mr Gerard on an old 
wall at Corstorphine Hill. 3 | 
