GENERA OF SHELLS. 75 



epidermis ; aperture entire, semioval ; lip sharp. 

 Columella produced inferiorly, subperforate at 

 base, with three transverse plaits. 



P. terebellum, dolabrata, plicata, corrugata, maculosa. 



SCALARIANA. 



Shell imthout plaits on the columella ; margins of the aper- 

 ture circularly united. 



The shells of the scalarianae have a tendency to form 

 a loose spire, so that the whorls are often disunited and 

 do not rest on one another. 



VERMETUS. Shell thin, tubular, loosely 

 spiral ; spire adhering by its apex ; aperture 

 circular ; margins united. Operculum. 



This shell greatly resembles a serpula : but its ani- 

 mal is not one of the annulata, but a true molluscum. 

 V. lumbricalis. 



SCALARIA. Shell subturreted, with longi- 

 tudinal, elevated, interrupted, nearly sharp ribs ; 

 aperture nearly circular ; the two margins unit- 

 ing and terminated by a thin, recurved rim. 



S. pretiosa, lamellosa, coronata, varicosa, communis, aus- 

 tralis, raricosta, multistriata, liheata, clathratulus. 



DELPHINULA. Shell subdiscoidal or coni- 

 cal ; umbilicated, solid ; whorls rough or angu- 

 lar. Aperture entire, round, sometimes trian- 

 gular; margins united, generally fringed or 

 rimmed. 



Distinguished from turbo by the united margins. 



