PINNA. 299 



propensity in the Mussel to open his shell, but not always 

 with equal success. A crow, seeing one clay an oyster with 

 his valves expanded on the beach, incautiously darted her 

 claw into the open shell, with the intention of dragging 

 forth the inmate ; but the oyster, aware of her design, in- 

 stantly closed his doors, and in so doing took the thief 

 prisoner. A gentleman found them in this situation, and 

 made a double capture. 



The genus Pinna is one of considerable interest, not 

 only on account of early poetic associations, but as re- 

 gards the new and peculiar structure of the shell, which, 

 instead o£ being solid and entirely coated with a firm nacre, 

 is composed of numerous perpendicular fibres, arranged 

 either in one laminal plate, or in several, one upon the other ; 

 the nacre itself is alone deposited in the central concavity 

 of each valve, the home of the indwelling mollusk. The 

 extended growth of the shell beyond the seat of animal ex- 

 istence, is elastic during the life of the occupant, but when 

 taken from the water and dried, it becomes hard and brittle. 



At least twenty different species are included under this 

 division : and here it is not unworthy of remark, that, 

 however individuals may vary in size and colour, the usual 

 form of their testaceous coatings always resembles that 



