63 



Genus 6. QUOYIA, Gray. 



Animal ; disc small, ovate, folded across and crumpled in front, 

 hind part furnished loith a semi-ovate operculum, side of the 

 body simple; proboscis short and ringed ; tentacles slender, 

 conical, far apart at the base ; eyes placed on short tubercles 

 at their outer base ; mantle simple, with a groove on the left 

 angle. 



Shell ; suhelongated, aperture short, slightly sinuated at the base, 

 columella peculiarly cut away at the top, interior finely grooved. 



■ The shell of tliis moUusk, figured by MM. Quoy and Gaimard in the 

 'Voyage de r Astrolabe', has very much the appearance of an elongated 

 Planaxis, and we learn from the characters of the soft parts above recited, 

 from Mr. Gray's ' Zoology of Beechey's Voyage ', that the animals of these 

 genera are in reality very closely allied. There is, however, a great dis- 

 similarity in the form of the shell, and the upper portion of the columella 

 is characterized by a curious broad groove or cutting away of the wliite 

 enamelled surface in place of any callosity ; from whence, I think, with 

 Mr. Gray, that it may be entitled to rank as a separate genus. 



Figure. 

 QuoYiA DECOLLATA. Plate 3. Fig. 18. — From Mr. Cuming's collection. 



Genus 7. NASSA, Lamarck. 



Animal; disc large and thin, nearly semicircular in front, termi- 

 nated on each side by a short ear-shaped appendage, hind ex- 

 tremity bifurcated ; head fattened, very large, with a conical 

 tentacle on each side, swollen at the outer side of the base and 

 having the eye situated at the top of the swollen portion. 



Shell ; ovate, slightly turreted, terminating at the base with a 

 deep sinus or very short canal ; aperture orbicular, angulated 

 at the upper part ; columella smooth, sometimes broadly effused, 

 luith a tooth or callosity at the upper part ; lip toothed, some- 

 times crenulated within. Opercidutn very small, horny. 



The Nassa are an interesting group, distinguished alike from the Buc- 

 cina, with which they were formerly associated, both in respect to the 



