BIVALVES. OSTREA, 



39 



generation and growth. By proper management their 

 multiplication becomes immense, and they are frequently 

 fornjed into large layers or beds, extending many miles. 

 These beds have often many proprietors, to whom they 

 generally, in favorable seasons, prove a submarine mine 

 of wealth. 



Almost all seas abound with Ostreae. The Ostrea Di- 

 luviana is found fossil in the calcareous mountains of 

 Sweden. 



