- 
90 
brown where exposed: there appear to be fragments of 
Entrochi also in the stone. The Planorbis resembles so 
much the fresh water Helices of Linnezus, thatall the spe- 
cies have been considered by some as inhabitants of fresh 
water, but this would seem an exception. 
Se EB 
PLANORBIS cylindricus. 
TAB. CXL.—Fig. 2. 
Spec. Cuar. Cylindrical, left side concentrically 
striated ; volutions three or four, adpressed ; 
aperture oblong quadrangular. 
eee 
Tut aperture of this shell is transverse, being wider 
than long, nearly in the proportion of three to two; the 
angles are obtuse, and it receives no indentation from the 
preceding whorl. The shell is about three times its 
thickness in diameter, and the left side has six or eight — 
obscure elevated striz. 
Some years since L was for a few hours at Cowes, on 
the Isle of Wight, and picked up a piece or two of stone 
which contained some of these shells, but as my time and 
immediate occupation did not allow me to extend my 
researches, I was content with what I had; this was in 
the severe frosty and stormy weather of February, 1808. 
I soon after visited by kind friend, Mr. Iremonger, at 
Wherwell vicarage, who gave me specimens he had from 
the Isle of Wight, on examining which I found several 
species of Planorbis and a Lymnea much resembling 
Helix stagnalis of Linneus, which I will add to this 
work hereaiter. 
The Planorbis here figured differs feom Helix contorta 
in the whorls being more equal and angular on each 
side and less numerous: the figures are about the natural 
size of the best Ehave seen. The remains are shelly with 
a smooth inside: the outside shows the lines of growth. 
