CONCHOLOGY. 167 



2. Cypraea. The Cowrie. 68 species. 



This genus derived its name from the Cyprian goddess, 

 on account of the beauty of its ponshed shells. They are 

 generally smooth, of great brilliancy of colour, and elegantly 

 marked with dots, zigzag lines, undulations, or stripes, and 

 covered with an enamel-like glaze. They are found buried 

 in the sand at the bottom of the sea, and are covered by the 

 animal with a thin membrane, which preserves the polish 

 and prevents other testaceous bodies from adhering to them. 

 This membrane consists of two parts, and arises on both 

 sides of the shell in the form of wings, furnishing the testa- 

 ceous and colouring matter ; in some species they do not 

 quite meet on the back of the shell, and the uncovered space 

 is marked by a coloured dorsal line ; when these membranous 

 wings overlap each other, this line is nearly obsolete. 



These shells often differ much with age ; at first in thick- 

 ness, then because the edges are thin, sharp, hardly dentated, 

 unless internally ; and, lastly, sometimes in the outline ; this 

 is because the two lobes of the mantle, by turning over the 

 primitive shell during the creeping of the animal, deposite 

 new calcareous matter. De Blainville cannot admit the hy- 

 pothesis of Bruguiere, that these animals can completely 

 abandon their shell to form a new one. 



Shell, when full grown and mature, is solid, oval, convex, 

 very smooth, involute ; the spire entirely posterior, very 

 small, often concealed by a calcareous layer deposited by the 

 lobes of the mantle, leaving in some species a small cavity 

 like an umbilicus ; aperture longitudinal, very narrow, slight- 

 ly curved, as long as the shell, with edges internally dentated, 

 and notched at each extremity. 



Shell, when young and immature, is very thin, the edges of 

 the aperture not dentated ; the right margin sharp and not re- 

 flected. 



Cypraea cerina. Cypraea tigris, 



C. exanthema. C. tigrina. 



