400* OSTRACEJ3 ; OYSTER ; ANOMIA. 



which thus accumulate, the race would speedily be extinguished 

 by the voracity with which Man preys upon them, were not the 

 destruction counterbalanced by the powers of multiplication 

 already noticed. But Man is by no means the only enemy to 

 the Oyster. Its body serves as food to many marine animals, 

 which have various methods of getting access to it, in spite of 

 its shelly defence ; from some of these it can secure itself by 

 closing its valves as soon as it is alarmed ; and against others 

 it has a more active means of defence, in the violent expulsion of 

 the water included between them, which (as it is itself fixed) 

 will frequently drive off its opponent. Various animals attack 

 it, also, by perforating its shell ; and to these also it can offer a 

 passive resistance, by depositing new shelly matter within. So 

 that even this lowly-organised being, commonly regarded as one 

 of the most vegetative of animals, is provided by its Creator with 

 such means as are necessary for its preservation, and doubtless 

 also for its enjoyment. 



1024. Nearly allied to the Oyster, but having also some 

 points of resemblance to the class of Palliobranchiata or Brachio- 

 poda, is the genus Anomia; which is re- 

 markable for the perforation of one of 

 its valves by a large aperture. This 

 orifice is intended to allow the passage 

 of a peculiar plug, usually more or less 

 calcined, the analogue of the byssus of 

 some other Mollusca, by which the ani- 

 mal adheres to foreign bodies. The 

 valves are thin and of irregular form ; 



FIG ess AXOMIA EPHIPPIUM being influenced by the surface on which 

 they grow. They are usually found at- 

 tached to the surface of other shells, especially those of Oysters. 



