

279 



point out those peculiar characters which eminently 

 distinguish them from that genus, and render their 

 separation expedient; but he classed them with 

 the G. Mitra: from both of which Lamarck has 

 properly divided them, as the following character- 

 istic distinctions never occur either in the Volutse 

 or the Mitrse — The right margin is thickened at the 

 outward side, forming a lip or marginal border; the 

 aperture occupies the whole length of the shell, and is 

 but slightly notched at the base; the plaits on the co- 

 lumella differ in position from those of the Volutee, be- 

 ing nearly of an equal size: the spire is extremely short 

 and sometimes altogether concealed, occasioning those 

 species to form a natural transition to the next genus; 

 they are marine shells, and have no operculum. It 

 appears probable that the inhabitant of these shells 

 covers the greater portion of the exterior with the 

 mantle of its body, in the manner of the Cypraeae and 

 some other genera, depositing successive layers of 

 testaceous matter in a similar way, as the examples of 

 this genus differ materially in thickness of substance. 



Shells with a projecting spire. 



Marginella glabella Marginella nubeculata 

 radiata « caerulesceii* 



