NOTES AND QUERIES. 79 
The tarn inhabited by L. involuta is called Lough Crincaum on the one- 
inch statute map. It is on a boggy plateau immediately under the apex of 
the mountain, which is a strictly preserved deer-forest. There is no path 
up, and the climb is a severe one. The pool is apparently not more than 
twenty feet across, and a quarter of it being situate close against the 
precipice of the upper mountain is inaccessible. My brother and I spent 
one hour and a half searching for specimens, but unsuccessfully. I heard 
afterwards they are only found under stones just where the stream runs out 
down the face of the mountain, but there are certainly none there at 
present, as neither the gamekeeper (who knows the shells well) nor 
ourselves could find them. Perhaps, owing to the unusual heat, they had 
retired into the mud in the middle of the pool.” In the succeeding 
number (p. 855), Dr. W. H. Evans thus comments on this communication : 
—“In ‘The Naturalist’ for November, 1864, I wrote a short account of 
an ascent of Cromaglaun, and the capture of a dozen of the Limnea 
involuta, in the summer of that year. I was there in wet weather, while 
Mr. Bendall was there at the close of the very dry summer of 1884, which 
circumstance will doubtless account for our different ideas as to the extent 
of the tarn. He gives it as twenty feet across ; when I saw it I feel sure 
that twenty yards would be much nearer the mark. The hot weather may 
also have had much to do with his want of success, for it is very possible, 
as he suggests, that the mollusks might shelter in the mud. Another cause 
may have operated: when I was there my guide told me that I should have 
found ‘a power more’ had I been there a week earlier, but that a gentleman 
from London had a few days before swept the tarn with a fine net, and 
secured agreat number.” He adds :—* This shell, although first described — 
by Mr. Thompson and very properly associated with his name, was 
discovered by my cousin, the late Dr. W. H. Harvey, for some time 
Professor of Botany in the Royal Dublin Society, and the author of a 
well-known work on British Seaweeds, ‘ Phycologia Britannica.’” 
The Resting Position of Oysters.—In books on Conchology, such as 
Woodward's ‘ Manual of the Mollusca’ and Jeffrey’s ‘ British Conchology,? 
it is stated that the Oyster rests in the natural state on its left valve, which 
is the larger and more convex. In this respect it is pointed out that Oysters 
differ from the animals belonging to the genera Pecten and Anomia, which 
rest on the right valve, the Anomias being firmly attached by muscle with 
the flat right valve applied closely to the surface of attachment. In his 
lecture on Oysters at the Royal Institution, which was published in Nos. 1 
wnd 2 of the ‘English Hlustrated Magazine,’ Prof. Huxley also states that 
Oysters rest on the left or convex valve, the flat right valve acting as a kind 
of operculum. Examination of Oysters from the Firth of Forth has con- 
vinced me that this statement is erroneous. I do not know on what 
evidence the current belief of conchologists is founded. ‘The evidence 
which appears to me conclusive is that the right flat valve is always quite 
