214 CASSIDIDiE. 



U.r. A. Candida, Mailer, pi. 22, fig. 9. 



The species of this genus hitherto discovered are but 

 few in number, and are from the Northern Seas ; the shells 

 are nearly devoid of colour, and are covered with a thin, 

 horny epidermis. Moller has described the animal, and 

 mentions the fact of the existence of eyes, which, how- 

 ever, are partly concealed under the skin ; the other genera 

 of this family are stated to be blind. 



Species of Amaura. 



caualiculata, Gould. cornea, Miill. 



Candida, Moll. 



Fam. CASSIDID.^. 



Lingual membrane short, broad, triangular, with many 

 rows of similar, lancet-shaped teeth, and a single small 

 dentated tooth in the central series. Mantle enclosed, 

 with a recurved siphon. Foot large, dilated. 



Operculum annular; nucleus in the middle of the 

 straight inner edge. 



Shell ventricose, subglobose, whorls often variced ; 

 aperture with a recurved canal ; outer lip thickened ; inner 

 lip wrinkled or granular. 



The " Helmet Shells," comprising many of the largest 

 known Gasteropods, form a very natural group ; they prin- 

 cipally inhabit the warmer regions of the globe. 



Genus CASSIS, Browne. 



Operculum oblong, narrow, small. 



Shell triangular, last whorl large, with irregular varices j 



