MOLLUSCA OR UNIVALVES. 



211 



from the coasts of New Holland, Tranquebar, 

 and from the Indian and Chinese seas ; they also 

 frequent the shores of the Mediterranean, near 

 Alexandria. The Solarium perspectivum, repre- 

 sented in the figure, is frequently called the 

 Staircase-shell. Specimens have been found 

 three inches in diameter ; and as they are ele- 

 gantly marked with black and straw colour, 

 they are often very beautiful objects. 



78. Rotella. — Shell small, outside smooth 

 and polished ; left lip very thick, 



and spreading over the under M^w} 

 surface so as to form a callosity ; N^ff^ 

 right lip sharp at the edge ; oper- ^~^^S 

 culum horny. Animal, head hav- 

 ing two very long and pointed tentacula, with 

 eyes at the base ; foot short. — 5 species, recent. 



From the Mediterranean, Indian, and Java- 

 nese seas. 



79. Trochus.— Shell conical; spire ele- 

 vated ; circumference of the whorls more or less 

 angulated, often quite sharp; mouth trans- 

 versely depressed ; edge of the outer lip dis- 

 united from the inner at the top ; inner lip 

 curved, rather oblique at the base ; sometimes 



p 2 



