Centimelers 



Figure o. — C. rhizophorae. On mangrove roots, Florida Keys. Dimensions: height 7 cm., lengtii 3.7 cm. (a) exterior; 



(b) interior of the shell. 



most smooth, sometimes covered with tubular pro- 

 jections. The color of the right valve is cream 

 buff with many radial chocolate bands; their 

 arrangements greatly variable. Muscle scar, situ- 

 ated near the center or a little dorsally, is white, 

 occasionally with olive-ochre spots. Margin of 

 the mantle is dark violet; the tejitacles are 

 arranged in two rows; those of the outer row are of 

 irregular size; the imier tentacles in a single row 

 are slender. 



The species, described from China by Gould, 

 occurs in Ariake Bay and in the bays of Okayama 

 Prefecture, Japan. It has established itself in 

 Puget Sound. 



Ostrea edulis Linne (fig. 9). This European 

 flat oyster is the type species of the genus Ostrea. 

 Shell round or oval; left valve larger and deeper, 

 slightly- bulging with 20 to 30 ribs and irregular 



concentric lamellae. Upper valve smaller, flat, 

 without ribs, with numerous concentric lamellae. 

 Beaks poorly developed. Ligament consists of 

 three parts; the middle part is flat on the left 

 valve and forms a projection on the right valve. 

 Muscle scar is eccentrically located, unpigmented. 

 Promyal chamber absent. Ostia and eggs rela- 

 tively large. Hermaphroditic and incubatory 

 mollusk, discharging eggs into the gill cavity. 

 Small numbers of European flat oysters were 

 introduced several years ago into the coastal 

 waters of Maine in Boothbay Harbor where they 

 survived and reproduced themselves. At present 

 the population is too small to be used commer- 

 cially. Recently the stock of European oysters 

 in Maine waters was increased by planting seed 

 raised from eggs fertilized and developed in the 

 Bureau of Commercial Fisheries Biological Labora- 



TAXONOMY 



