338 
ISLAND LIFE. 
[part II. 
peculiarity of the soil and water in the former island, have really led to 
the production or preservation of a well-marked variety of insect. 
Land and Fresh-water Shells . — As regards the land and 
fresh-water mollusca it seems difficult to obtain accurate infor- 
mation. Several species have been recorded as British only, 
but I am informed by Mr. Gwyn Jeffries that most of these are 
decidedly continental, while a few may be classed as varieties of 
continental species. According to the late Mr. Lovell Reeve 
the following species are peculiar to our islands ; and although 
the first two seem extremely doubtful, yet the last two, to which 
alone we accord the dignity of capital type, may not improbably 
be peculiar to Ireland, being only found in the remote south- 
western mountain region, where the climate possesses in the 
highest degree the insular characteristics of a mild and uniform 
temperature with almost perpetual moisture, and where several 
of the peculiar Irish plants alone occur. 
1. Cyclas pisidioides. — A small bivalve shell found in canals. Perhaps 
a variety of C. corneum or C. rivicola according to Mr Gwyn Jeffries. 
2. Assiminia grayana. — A small univalve shell allied to the periwinkles, 
found on the banks of the Thames between Greenwich and Gravesend, on 
the mud at the roots of aquatic plants. 
3. Geojialacus maculosus. — A beautiful slug, black, spotted with yellow 
or white. It is found on rocks on the shores of Lake Carogh, south of 
Castlemain Bay, in Kerry. It was discovered in 1842, and has never been 
found in any other locality. An allied species is found in Portugal and 
France, which Mr. Gwyn Jeffries thinks may be identical. 
4. LimNjEA involuta. — A beautiful pond-snail with a small polished 
amber-coloured shell, found only in a small alpine lake and its inflowing 
stream on Cromaghaun mountain near the lakes of Killarney. It appears 
to be a very distinct species, most nearly allied to L. glutmosa which is 
not found in Ireland. It was discovered in 1832, and has frequently been 
obtained since in the same locality. 
The facts — that these two last-named species have been known 
for about forty or fifty years respectively, that they have never 
been found in any other locality than the above named very 
restricted stations, and that they have not yet been clearly iden- 
tified with any continental species, all point to the conclusion 
that they are the last remains of peculiar forms which have 
everywhere else become extinct. 
Peculiarities of the British Flora . — Thinking it probable 
