184 LIMNiEADiE. 



yellowish hue, speckled with opake sulphury clots, and very 

 slimy to the touch ; with them, when in the water, it covers 

 its shell, hut instantly withdraws them on being touched. 

 The tentacles and foot are similar to those of other Lym- 

 tkei. Van Beneden has investigated its anatomy, and 

 shown that there are some remarkahle peculiarities in its 

 nervous system, having relation to its dilated mantle. 



It is a scarce shell, though plentiful where it occurs. It 

 is found in the south-eastern English counties, but very 

 locally : it occurs in Windermere lake, but in one part only, 

 according to Mr. Winstanly. Mr. Gibhs, of the Geolo- 

 gical Survey, has communicated to us fine specimens from 

 Bala Lake, in North Wales. 



L. ixvolutus, Harvey. 



Almost membranaceous, transparent ; ovate, with the spire 

 truncated or sunken. 



Plate CX XII. fig. 11. 



Limneus involutus, Harvey, MS. Trans. Linn. Soc. vol. xvii. p. 559 (no desc.). — 

 Alder, Mag. Z. and B. vol. ii. p. 115 (no desc). — Thomp- 

 son and Coodsir, Ann. N. II. vol. v. p. 22. 



Amphipeplea itivoluta, Gray, Manual L. and F. \Y. Shells, p. 2-15, pi. 12, f. 147. 



Liimnaa „ Brown, Must. Conch. G. B. p. 29, pi. 18, f. 5. 



Shell rather small, subtruncated-ovate, extremely thin, 

 more or less glossy, transparent, fulvous horn-coloured. 

 Body composing nearly the entire shell, the spire, which 

 consists of scarcely three coils, that are remarkably small 

 and merely convex, being flat or a little sunken ; surface 

 of the last volution not equably ventricose, but rather more 

 planulate above ; basal declination gradual, convex. 

 Mouth of a curved pear-shape, occupying about three- 

 fifths of the ventral area ; very broadly rounded, and a 



