39 



fabled to have risen in one of them from the bottom of the sea, — an allegory 

 which has afforded matter for several of the most exquisite compositions of 

 ancient as well as of modern artists. On antique gems and cameos, Venus, 

 under various characters, Amphitrite, Doris, and other goddesses and nymphs, 

 in the train of Oceanus, frequently appear upborne upon the waves. Driden 

 thus alludes to the pagan allegory : 



Albion 

 Was to Neptune recommended ; 

 Peace and plenty spread the sails; 

 Venus, in her shell before him, 

 From the sands in safety bore him. 



This genus contains at present 27 species, which present considerable 

 diversity of character. Its divisions are two, divided into families. 



DIVISION I. Shell equivoke. 



Family 1st. With longitudinal ribs, gaping at the posterior slope. 



Scientific name. Locality. Scientific name. Locality. 



Gigas, Red Sea, Amboyna, Hippopus, East Indies, China, 



China, New Holland. Amboyna. 



Family 2d. With longitudinal ribs, posterior slope closed. 



E. Ind., Med., Senegal. 



Family 3d. Shell longitudinally ribbed, having an ovate chamber in the interior 



of each valve. 



Concaraerata, Cape of Good Hope. 



Family 4th. Shell decussated or transversely striated, without ribs. 



Semiorbiculata, Arabia. Oblonga, Guinea, Pulo, Condore. 



Cordata, do. Coralliophaga, E. Indies, in Coral. 



Family 5th. Shell tuberculated. 

 Plumbea, South Seas. 



