140 



PATELLID^E. 



Shell concave underneath, without regular spire, en- 

 veloping a conic animal. 



XXVII. ANCYLUS. 



Shell thin, concave underneath, elevated into an 

 oblique cone, without regular spire or pillar ; the 

 point rather acute, and inflected posteriorly : aper- 

 ture oval or oblong, very entire at the margin, 

 and without operculum : muscular impression sub- 

 orbicular, and emarginate anteriorly. 



Separated from the Patella, which is a marine shell, 

 and generally furnished with one or more volutions 

 at the point of the cone ; and whose apex or point 

 turns anteriorly. 



125. ANCYLUS Jluviatilis. Shell conoid, with the 

 point recurved and near one end : aperture round- 

 ish-oval. 



