14 BULLIDiE. 



Genus VOLVULA, A. Adams. 



Shell sub-cylindrical, beaked at both ends ; spire none ; 

 aperture narrow, linear, extending posteriorly beyond the 

 body-whorl, acuminate in front ; inner lip with a single 

 obsolete fold at the fore part; outer lip acute, produced 

 and pointed posteriorly. 



Ex. V. rostrata, A. Adams, pi. 56, fig. 10. 



The animal of this genus is unknown, but it is most 

 probably to be referred to this family. The Rhizorus of 

 Montfort, from the figure and description, has a variegated 

 shell with a sunken spire, and appears to be founded on 

 a small species of Volva. Volvula differs from Volvaria 

 in the spire being entirely concealed, and in having but a 

 single fold at the fore part of the inner lip. 



Species of Volvula. 



acuminata, Bnty. striatula, A. Adams. 



angustata, A. Adams. mucronata, Phil. 



etmrnea, A. Adams. granuluin, Phil. 

 rostrata, A. Adams. 



Fam. BULLID^. 



Teeth, central one, lateral numerous, uniform, in an arched 

 series. Animal partly investing, but not entirely cover- 

 ing, the shell. Tentacular frontal disk expanded, emar- 

 ginate behind ; eyes none, or sessile on the middle of the 

 frontal disk. Mantle with the right margin thickened, the 

 left thin, adhering to the body-whorl of the shell. Foot 

 with the sides greatly developed, often reflexed and cover- 

 ing the sides of the shell, or expanded for swimming. 

 Gizzard usually armed with calcareous or horny plates. 



Shell external, involute, more or less covered by the 

 reflexed lateral lobes of the foot. 



