NATURAL HISTORY. 



471 



Family, Mytilidse. (Gr. MurtApr, a Mussel.) 



J * V * f 



MTTILUS. 



Edulis (Lat. edible], the Edible Mussel. 



The river mussels occasionally produce pearls of some value. 

 The nacre of these mussels is of a beautiful azure blue. 



Order, CIRRHOPODA.(G\\ Hevrt, five; llaapa, a plate.) 



PEXTALASMIS. 



Anatifera (Lat, Goose-bearing), the Bernide. 



At first sight, the Bernicle bears a close resemblance to a 

 mussel-shell fixed to a long stem. On a closer examination, 

 however, the difference is at once apparent. The shell is in 

 fact composed of Jive pieces, and through the aperture of the 



