MOLLUSCA OR UNIVALVES. 243 



markings, render them interesting. They 

 never attain a large size, and the greater 

 number are litoral shells. They are some- 

 times sinistral. 



109. Nassa. — Shell globular or oval, ac- 

 cording to the spire, which is some- 

 times short, sometimes rather long; 

 mouth oblong, notched; inner lip 

 thickened, and spread out, occasionally 

 very large ; right lip often wrinkled ; 

 operculum horny. Animal, head large; pro- 

 boscis short, or altogether wanting ; two tenta- 

 cula, with eyes in the middle ; foot very large. 

 — 9 species recent, and 2 fossil. 



They abound in the South of Europe and 

 the East Indies ; and some are also found on 

 our coasts. They are occasionally seen on the 

 sand or reefs, feeding on the Mactra, which 

 they effect by piercing the shell with their 

 proboscis, making an extremely regular round 

 hole, and extracting the contents through the 

 aperture thus formed. 



110. Eburna. — Shell oval, smooth ; mouth 

 oblong and notched; left lip thickened, right 

 thin; operculum horny ; and an umbilicus. Ani- 



R 2 



