Cent i meters 



Figure S. — C. rivularis. Puget Sound. Introduced from Japan with the seed of C. gigas. Dimensions: height 10.7 

 cm., length 10.5 cm. (a) exterior of lower (left) valve; (b) interior of upper (right) valve. 



Centimeters 



Figure 9. — O. edutis, European flat oyster introduced from Europe to Boothbay Harbor, Maine. Dimensions: height 

 9 cm., length 11 cm. (a) exterior of the left (lower) valve; (b) interior of the right (upper) valve. 



tory at Milford, Conn. Prodissoconch shown in 

 fig. 350 ch. XVI. 



0. lurida Carpenter (fig. 10). Shells from 2 to 

 3 inches in height, with coarse concentric lines. 

 Inner side of valves usuallj^ olive-green. Promyal 

 chamber absent. Hermaphroditic, incubatory, 



eggs retained in the gill cavity until fully de- 

 veloped larvae are formed and discharged into the 

 water. Inhabits the tidal waters of the Pacific 

 Coast of North .America from Alaska to Lower 

 California. (Prodissoconch shown in fig. 351, 

 ch. XVI.). 



TAXONOMY 



11 



