THE OYSTER. 317 



Description. 



CHAP. XL 



' The prickly star creeps on with full deceit, 

 To force the ouster from his close retreat." 



JONES'S OPPIA*. 



THE OYSTER. 



OYSTERS are bivalve shell fish, having the 

 valves generally unequal. The hinge is without 

 teeth, but furnished with a somewhat oval cavity, 

 and mostly with lateral transverse grooves. They 

 adhere to rocks, or, as in two or three species, to 

 roots of trees on the shore. 



These shell fish are formed with organs of life 

 and respiration, with intestines which are very 

 voluminous, a liver, lungs, and heart. They are 

 self-impregnated, and the shells, which they soon 

 acquire, and to which they are strongly attached 

 both above and below, serve them for their fu- 

 ture habitation. Oysters breathe by means of 

 gills; they draw the water in at their mouth, a 

 small opening in the upper part of the body, 

 drive it down a long canal that constitute the 

 base of the gills, and so out again, retaining the 

 air for the necessary functions of the body. 



