70 LIMNJEAD^. 



Amphipeplea involuta, Gray. 



This rare Limnceus has only been discovered in one 

 locality. It is thus described by the late W. Thomp- 

 son, " Shell polished, extremely thin, of a pale amber 

 colour, with coarse longitudinal striae. It approaches 

 L. glutinosus more nearly than any other species. The 

 aperture is very large, wide at the base and extending 

 to the apex ; margin reflected only when it joins the 

 pillar." About five lines in length and three and a 

 half in breadth. 



Hah, A small Alpine lake, at Cromaglaun moun- 

 tain, near Killarney. ^ 



Ancylus. Geoffroy. 



Shell — Limpet sJiaped, conical ovate, simple and recurved ; 

 aperture ample, interrupted ; apex on the left side by a 

 semi-lunar scar ; no operculum. 



Animal — Conical, filling the whole of the shell, head Iroad, 

 tentacles triangular ; mantle simple, not reflected. 



A. FLUvTATiLis. MulUr. PI. VIT, fig. 37. 



Shell conoid ; the apex recurved and near one end, bent to the right ; 

 aperture oval. 



Patella lacustris, Linn. 



The fresh water limpets, for so these shells are de- 

 nominated, are very much like the marine Patellce, and 

 were for a long time placed by naturalists under that 

 genus. The shell of fluviatilis is about a quarter of an 

 inch in length, two lines and a half in breadth, and 

 almost as high as long. It is semi-transparent, but 

 covered with an olivaceous or black epidermis, slightly 

 striated. The inside of the shell bluish white and 

 glossy. Animal light grey. 



Hab. Abundant on stones, in clear brooks or run- 

 ning streams, in all parts of the British Isles. 



A. OBLONGUS. Lightfoot. PL VII, fig. 38. 



Shell elongated, oblong, compressed ; apex in the middle and very 

 slightly recurved, bent to the left ; aperture oblong. 



