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ANCYLUS. 



Muller, Hist. verm. 



TESTA tenuis, oblique conica, patelliformis ; 

 apice subacute, postice inflexo; apertura ovali, 

 marginibus simplicissimis. 



A LITTLE Genus of fresh water shells, first separated from 

 the Linnean Patella by Miiller. Several succeeding au- 

 thors have seen the propriety of this separation, and have 

 consequently adopted it : nevertheless it is not easy to 

 point out any good character by which it may he distin- 

 guished from the true Patellse, if we except the position 

 of the apex which in this is turned backwards, and in 

 Patella forwards ; and the differences in the little animal 

 inhabitant, which in Ancylus nearly resembles that of Lim- 

 iiea, which differs very materially from that of Patella, and 

 for this reason w e approve of Draparnaud's placing it next to 

 Limnea in his systematic distribution, and wish Lamarck 

 had in this respect followed Draparnaud : it is, how^ever, 

 but justice to the last-mentioned celebrated conchologist 

 to add, that he has only placed it provisionally as an 

 appendix to the family which he designates by the term 

 Calyptraciens. Shell thin, obliquely conical, patelliform ; 

 apex or vertex, rather pointed, not lengthened nor spiral, 

 turned backwards, and if w e observe the shell in an ana- 

 logous position to that in which w e are generally accus- 

 tomed to place it, we shall find that its point is also turned 

 a little upwards : we have in our plate assigned this 

 position to both species, in order the better to explain 



