222 



PLANAXIS. 



BUCCINUM SULCATUM. Bom. 



Sowerbys Genera, No. 12, plate 3. 



These are marine shells allied to the G. Phasianella, 

 from which they are distinct, having the base of the co- 

 lumella truncated as in the Melanopsis, and would have 

 been yet more different if they had not possessed an 

 operculum, as Lamarck imagined ivas the case. The 

 shells of this genus are generally small, transversely 

 grooved on the exterior; of an oval, conical form; 

 solid ; aperture ovate ; columella flattened, truncated 

 at the base, separated on the right margin by a nar- 

 row sinus or channel; the interior surface of the right 

 margin grooved or rayed with a callosity running be- 

 neath the summit, appearing in that respect allied to 

 the G. Buccinum and G. Purpura. Sowcrby in his 

 Genera of Shells, observes, that he has seen one spe- 

 cies with a thin horny operculum, (a circumstance with 

 which Lamarck was unacquainted), and considers them 

 more nearly allied to the Buceina and Purpuras, than 

 tothePhasianellap, in consequence of the callosity which 

 runs under the summit of their right lip. 



Planaxis sulcata Planaxis undulata. 



