MOLLUSCA OR UNIVALVES. 193 



small protuberances at their base ; foot large. — 

 There are 3 species, recent. 



These Mollusca are fluviatile, inhabiting the 

 clear rivers of India, the Isle of France, &c. : 

 they creep well on the rocks, and do not con- 

 tinue fixed to one spot, as the Patella. In the 

 Isle of France they are made into broth for 

 invalids. 



60. Neritina. — Shell thin, having no um- 

 bilicus, and being globular 

 or oval ; mouth semicircular ; 

 left lip flattened and sharp, 

 right lip destitute of teeth. 

 Animal, head large, having 

 two tentacula, with eyes at the base; foot 

 short. — 54 species recent, and 9 fossil. 



The Neritince are fluviatile, and are found in 

 the East and West Indies, the Isle of France, 

 &c. ; they are exceedingly pretty shells, the 

 lines and marks, when looked at through a mi- 

 croscope, being often very beautiful. They are 

 worn as ornaments by the Indians. The Neri- 

 tina corona is coated with a black epidermis, 

 and has a row of long sharp spines : the Neri- 

 tina viridis, a very small green species, found in 

 o 



