214 
LIMN^AD^. 
one, marked by a deep suture, and ending obtusely ; 
the larger volution regularly striate ; pillar without 
umbilicus. 
This shell appears to have a very extended range, 
being found in Sweden in the north, and Syria in 
the south. 
97. 2. Amphipeplea involuta. Involuted Membrane 
Shell. — Shell ovate, subglobose, truncated, thin, 
transparent, very brittle ; spire flat, of three or 
four very gradually enlarging whorls, (t. 12. 
f. 147.) 
Limneus involutus. Harvey; Thompson^ Linn, 1834; 
Alder ^ Cat. ii. 215.; Thompson and Goodsir., Ann. N, H, 
V. 22. — Limnaeus involutus. Forbes and Hanley B. A. 
iv. 184. t. 122. f. 11. — Amphipeplea involuta. Gray.^ 
Man. 245. t. 12. f. 147. — Limnsea involuta. Brown^ 111. 
t. 18. f. 5. 
Inhab. lakes, Ireland. 
Shell very thin, and polished like the former, but 
is easily distinguished from it by its more ovate 
shape and truncated tip, produced by the flat or 
sometimes slightly concave form of the spire. It is 
easily known from Physa fontinalis^ which it greatly 
resembles, in not being reversed, by the peculiar 
form of the spire, and the plait on the pillar lip. 
Professor Forbes thinks that this shell may be 
some monstrous yet permanent variation of a mere 
ordinary Limnceus. (See Brit. Moll. 185.) 
On my writing to Mr. Thompson, of Belfast, 
respecting this shell, he has kindly furnished me 
with the following particulars, which I print en» 
tire : — - 
