GENUS DOLIUM, LAMARCK. 



THE TUN. 



Shell thin, ventricose, inflated, generally globular, rarely 

 oblong, encircled with ribs ; spire short ; right lip crenulated, 

 and sometimes denticulated throughout its whole length ; aper- 

 ture oblong, very large, emarginated inferiorly ; columella chan- 

 neled ; no operculum. 



Testa tenuis, ventricosa, inflata, ssepius subglobosa, raro oblonga, trans- 

 versim cingulata. Spira brevis. Labrum per totam longitudinem denta- 

 tura vel crenatum. Apertura oblonga, amplissima, basi emarginata. Oper- 

 culum nullum. 



Animal very large, so as scarcely to be contained within its 

 shell ; the head is broad, swollen before, supporting two long, 

 slender, obtuse, distant tentaculae, dilated towards the base, 

 where the eyes are situated. The mouth is large, muscular, 

 strong and retractile. The respiratory tube is pretty stout ; its 

 cavity is capacious, entirely open, provided with two branchiae 

 placed on the left side, the larger of which, describes a pretty 

 large semicircle. The trunk is cylindrical, very much devel- 

 oped, flexible, capable of being turned in every direction at the 

 will of the animal, and of elongating itself in a remarkable 

 manner ; it is furnished internally with several rows of hooks. 

 The foot is ovate, large, fleshy, bordering all parts of the shell ; 

 it is rounded, widened, lobed and dilated before, with a hori- 

 zontal furrow. The posterior extremity has no trace of an 



Dolium. A 



