MOLLUSC A OR UNIVALVES. 235 



grooved, and often spotted with round tu- 

 bercles ; operculum horny. Animal like that 

 of the Cassis. — 5 species recent, and 2 fossil. 



These shells chiefly come from the seas of 

 warm latitudes ; one or two species are found 

 in European countries. 



100. Oniscia (Sowerby). — Shell oblong, 

 rather obtuse ; spire short, base rather 

 pointed; mouth longitudinal; canal 

 very short ; outer lip thickened, 

 toothed within; inner. lip expanded 

 and covered with raised spots ; outside 

 ribbed. Animal not known. — 3 species recent, 

 and 1 fossil. 



It is litoral in its habits, and is found in 

 sand in the South Seas. 

 I 101. Cassis. — Shell large and heavy; spire 

 short; mouth either long and 

 narrow, or rather oval, termi- 

 nated by a short canal ab- 

 ruptly curved towards the back 

 of the shell ; both lips generally 

 toothed and flattened; opercu- 

 lum horny. Animal, head large, 

 with a very short proboscis, and two tentacula 



