ANCYLUS. 185 



little reflected, below ; gradually and acutely contracted 

 above by the moderate swell of the body, and the slant- 

 ing inclination of the outer lip, which latter is arcuated 

 (especially anteriorly) ; enamel of the inner lip diffused 

 but very thin ; pillar extremely narrow, arched, the fold 

 not very conspicuous. No umbilical chink. Length five 

 lines and a half; breadth three lines and a half. 



The external characters of this animal, as displayed 

 when living, have not been fully described ; some account 

 of its anatomy has, however, been published by Professor 

 Goodsir. This remarkable shell, which after all may be 

 some monstrous yet permanent variation of a more ordi- 

 nary Limnaus, was discovered by Professor Harvey, in a 

 small Alpine lake on Cromaglaun Mountain, near Killarney, 

 where it was afterwards taken by our lamented friend, 

 Mr. W. Thompson, of Belfast, and by Dr. Robert Ball* 



ANCYLUS. Geoffroy. 



Shell limpet-shaped, thin, horny, ovate or oblong, de- 

 presso- conical, with a posterior, slightly and obliquely 

 recurved apex. Aperture ample, with entire margin ; inner 

 surface exhibiting a laterally-interrupted semilunar scar. 

 No operculum. 



Animal with a broad head and two triangular tentacles 

 with the eyes at their bases. Mantle simple, not reflected. 

 Foot ovate, ample. Tongue armed with rows of numerous 

 hamate teeth, much incurved, flanking narrow, compressed 

 central denticle. 



The striking resemblance of the shells of these fresh- 



* The Turbo rivulus of authors (Mont. Test. Brit. p. 331 ; Maton and Rack. 

 Trans. Linn. vol. viii. p. 186; Turt. Conch. Diction, p. 2:29), was solely consti- 

 tuted from an execrable figure in Walker's Testacea (f. J7), apparently intended 

 for a member of this genus. 



VOL. IV. B li 



