73 



Mactra chinensis Philippi ( see below), Spirula sachaliensis (Schrenck) 

 (see below), and Spisula voyi (Gabb) (larva not described) inhibit Peter the 

 Great Bay. 



Myidae 



The veliconcha shell is equivalve. The posterior end is broader than the an- 

 terior. The dorsal margin is straight and slopes markedly, while the ventral 

 margin is round. The umbones are flat and low. There is one provincular tooth 

 on each valve. One flange occurs on the right valve (posterior) and another on 

 the left (anterior). The ligament is posterior. Eyes are absent. Soft body with 

 dark pigmentation. 



Mya japonica Jay (see below) and Mya truncata (Linne) (see below) 

 inhabit Peter the Great Bay. 



Pholadidae 



The veliconcha is large. The shell is equivalve, convex, and inequilateral. The 

 anterior end is slightly longer than the posterior. The margins are smooth and 

 broadly roundish. The dorsal margins are short, round, and slope abruptly. In 

 the early veliconcha the umbones appear roundish but later become knob- 

 shaped and considerably raised. The hinge has two teeth of the same size on 

 the left valve and two on the right, one of which is longer and central in 

 position while the second, smaller tooth is simated in the anterior part of the 

 hinge line. The small teeth on the left valve are separated by a wide socket 

 for the central tooth of the right valve. Flanges occur on the left valve and 

 crests on the right. The ligament is posterior. The margins of the valves are 

 edged with a dark band. A pallial line is present. Eyes are absent. The umbo 

 is purplish-red. The anterior adductor is slightly larger than the posterior. 



Barnea japonica (Yokoyama) (see below) and Zirfaea crispata (Linne) 

 (see below) inhabit Peter the Great Bay. 



Teredinidae 



The shell of the veliconcha is round and highly convex. As it grows, the shell 

 becomes somewhat oval and dorsoventrally produced. The anterior and poste- 

 rior ends are broadly rounded and symmetric. The height of the shell is slightly 

 greater than its length. The dorsal margins are short, round, and slope sharply. 

 The umbo is round, becoming knob-shaped in late veliconcha. The hinge has 

 large rectangular teeth — three on the right valve and two on the left. Flanges 

 occur on the left valve and crests on the right. The ligament is posterior. The 

 surface of the shell has concentric striation. The larva is dark colored (from 



