GASTEROPODA. 



127 



growth, and having the imperfect rudiments of a spiral 

 nucleus at one extremity. Animal, with a broad head, 

 ending in a narrow bilobed snout, furnished with a re- 

 tractile proboscis; tentacula two, triangular, or ear-shaped, 

 their inner bases connate, or nearly so; eyes placed at 

 the inner sides of the tentacula; tongue probably un- 

 armed ; anterior and upper margin of the foot furnished 

 with a distinct fold or mentum ; foot triangularly lan- 

 ceolate, short in proportion to the length of the shell ; 

 operculigerous lobe apparently simple, but, according to 

 Loven, furnished with a minute conical process on each 

 side.* — About 20 species ; also fossil. 



Elegant shells of very small size, ribbed longitudi- 

 nally, and some having spiral raised lines also. 

 There are about seven British species. 



Nerikea. Defrance. — Shell elongated, cy- 

 lindrical, having many whorls ; aperture with 

 a canal, the interior having ridges, both on the 

 inner and outer lip. — 150 species, fossil. 



No other shell resembles these, and a sec- 

 tion presents a curious appearance from the 

 prominent folds on the three upper angles of 

 the subquadrate aperture, f 



Family 23. — E ULIMA CEA. 



The animals are imperfectly known, but are distin- 

 guished from those of Pyramidellacea by the long, slender, 

 cylindrical tentacula. The shell is turret-shaped, formed 

 of numerous whorls ; the aperture oval and entire. — 

 Marine. 



* Forbes's British Moll. 



f Sowerby, 



