80 Beautiful Shells, 



morsel has bceii extracted be taken in the hand, it 

 may be noticed that one is much thinner, smoother, 

 and flatter than the other: this is the side most 

 exposed to the action of the water; the rougher 

 and rounder side is that which is attached to the 

 rock or other substance to which the animal forms 

 an attachment that is usually life-long. The two 

 portions of the shell are joined together by a hingo 

 of curious workmanship, which is formed of tho 

 inner layer of the shell, and strengthened by a 

 ligament which is wonderfully elastic; when the 

 shell is drawn together by the abductor muscles, the 

 ligament is at full stretch, and as soon as they relax 

 at all, it contracts, and causes the shell to gape. 

 This process is repeated as often as may be neces- 

 sary for the safety and sustenance of the animal 

 within, whose mouth is situated at the narrowest 

 part of its habitation — namely, near the joint of tho 

 hinge which connects its upper and under shell. The 

 anatomical structure of the Oyster is more perfect 

 than would be supposed, from its apparently low 

 state of organization ; it has a heart, liver, and in- 

 testinal canal, and a bag near the moutli, which 

 answers the purpose of a stomach. Its breathing 

 organs are gills, closely resembling those of most 

 other fish; it has little vessels which convey the 



