214 LIMNiEAD^. 



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; Tliompsnn, Linn. Tro/zs. 1834 ; 

 Alder, Cat. ii. 215.; Thompson and Goodsir, Ann. N. H. 

 V. 22. — LimnEeus iavolutus. Forbes and Hanley, B. A. 

 iv. 184. t. 122. f. 11. — Amphipeplea involuta. Gray., 

 Man. 245. t. 12. f. 147. — Limnaea involuta. Brown, 111. 

 t. 18. f. 5. 



Inhab. lakes, Ireland. 



Shell very thin, and polished like the fonner, 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 fontinalisy 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 LimnoBus. (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 : — 



