TRIDACNACEA. 307 



as a striking proof that the tender mercies of the Creator 

 are over all His works. That gracious Beings who sustains 

 the planets in their courses, takes care of the helpless Finna, 

 and assigns him a companion, who, himself houseless and 

 defenceless, amply compensates, by activity and quick- 

 sightedness, for the deficiencies of his blind protector. 



Family V. Tridacnacea. 



Methinks that quiet spirit. 

 Which broodeth o'er the rocks and sounding shore. 

 Blends with the awful rushing of the waters. 

 And fills this lonely spot with holiest musings. 



The Tridacnacea exhibit a well-defined assemblage of 

 characters, and may be easily distinguished. They are 

 generally of considerable size, living attached to rocks and 

 corals, by means of a strong byssus ; and as they are readily 

 found in open places, they are brought to this country in 

 great abundance. Their shells are solid, transverse, equi- 

 valve, and more or less gaping at the lunule, beneath the 

 umboes ; the ventral or outer margins of the valves being 

 deeply sinuated, and interclosing with each other. The 

 muscular impression is duplex or bipartite, situated about 

 the centre, and spreading nearly to the ventral margin. 



X 'Z 



