7 6 
die bottoms of the lakes of Kinnairdy in Scotland, when 
they were drained, there were found beds of a kind of 
shelly tufa, varying in thickness from two to six feet, 
covered by sulphureous peat from two to ten feet deep; 
below this is sand, then clay, and frequently beneath the 
clay is another thin layer of the shells. Specimens of these 
were sent me by my good friend Charles Lyell, Esq. 
in 1808. I found the shells to be the same species as those 
which at present frequent such lakes. The masses are 
three or four inches square, very friable, light and 
delicately white, except here and there a brownish or 
reddish stain; the shells are delicately preserved in a 
similar way to those found near Paris, and which so much 
resemble the Helix planorbis, Linn. The Isle of Wight 
shells, which are somewhat similar, but as I shall hereafter 
show, distinct, come next in the order of preservation; in 
1807, the Rev. G. R. Leathes brought me specimens from 
the Isle of Wight, in which, besides the Helices resembling 
planorbis, are casts of shells of the present genus in a clayey 
marie. In the Sussex marble also there are often casts of 
the same genus, and the late General Davies, in 1806, 
brought me similar ones, found two feet under clay, on the 
road from Rathersden to Ashford in Kent. Mr. Smith 
informs me that the clay there is beneath the chalk. From 
these different localities of shells, apparently of the same 
genus, we must conclude, either that analogy is not sufficient 
to prove that these fossils are of fresh water origin, or else 
that there are more fresh water formations than are generally 
supposed. 
