164 THE OYSTER FAMILY. 



varies greatly, though its normal shape is circular. 

 The lower valve is smaller than the upper, and as in 

 the last species it is pierced for the strong plug which 

 attaches the animal to a rock. Through this hole 

 you can see the large muscle scar inside the upper 

 valve, and can notice its curious, radiated structure. 



The shells are pearly within, and are generally of a 

 greenish tinge. The outside is marked by irregular 

 radiating ridges. Sometimes this species grows to 

 the size of a large oyster, but ordinary specimens are 

 about two inches across. When the structure and 

 the color of the pearl are once known, even a frag- 

 ment of this shell can be readily recognized. This 

 species is found along the whole coast, particularly 

 at the north. 



Ostrea hirida, Cpr., Os'-tre-a lu'-ri-da. This is 

 the common native oyster of this coast, and is well 

 known as distinct from the Eastern oyster, Ostrea 

 Virginiana^ Lister, which is brought here from Balti- 

 more and other Atlantic ports. The young oysters, 

 about an inch long, easily endure the seven or eight 

 days of travel across the country, and when planted 

 in our bays, they thrive and grow rapidly. In three 

 or four years they are ready for the market, i^lthough 

 they spawn abundantly, but few of the young survive, 

 probably on account of the coldness of the water; 

 though occasionally a true, young Eastern oyster may 

 be found attached to some old post, showing that at least 

 a few of the eggs have developed properly. 



The specimens of our native species, O. hirida^ 

 are small, with rather dark-colored shells, sometimes 

 stained with purple. The greatest dimension of the 

 shell is about two inches. The variety cxpaiisa^ Cpr., 

 is nearly circular, and is attached by the whole sur- 



