72 



(Carpenter), Saxidomus purpuratiis (Sowerby), Dosinia japonica (Reeve), 

 Mercenaria stimpsoni (Gould), Protothaca jedoensis (Lischke), Protothaca 

 euglypta (Sowerby), and Callithaca adamsi (Reeve); their larvae have not been 

 described. 



The larva of Ruditapes philippinarum (Adams and Reeve) has been de- 

 scribed (see below). 



Cultellidae 



The morphology of the larvae of this family is identical to that of the family 

 Solenidae. The principal difference is that in the veliconcha of the family 

 Cultellidae, the shoulders are straight, sloped, or slightly concave. 



Siliqua aha (Broderip and Sowerby) (see below) inhabits Peter the Great 

 Bay. 



Solenidae 



The shell of the veliconcha is equivalve, oval, and anteroposteriorly elongate. 

 The anterior end of the shell is equal in length or slightly longer than the 

 posterior. The umbo is broadly roundish. The hinge system consists of two 

 large teeth (one on each end of the hinge line) on the right valve and corre- 

 sponding sockets on the left valve. Between the sockets of the left valve, a thin 

 row of very small sharp or blunt teeth occurs which, during closure of the 

 shell, enter the alveoli on the right valve. The ligament is external. A pallial 

 line is present on the inner surface of the valves. Eyes are absent. 



Solan krusensterni Schrenck (see below) inhabits Peter the Great Bay. 



Mactridae 



In the veliconcha stage the larva is ovate or rounded-oval. The shell is equivalve. 

 The anterior end is longer and more pointed than the posterior. As the posterior 

 end is ventrally more produced than the anterior, it is considerably broader 

 than the anterior. The shoulders are slightly rounded and slope slightly; the 

 anterior shoulder is longer than the posterior. The umbo is broad and roundish, 

 sometimes becoming triangular later. The hinge system has one rectangular 

 tooth on the right valve and two teeth of different size on the left valve. In 

 the anterior part of the hinge line a large lobate tooth occurs. There are also 

 lateral teeth in the form of tubercles on both sides of the hinge on each valve. 

 In some species of Mactridae, the hinge is similar on both sides, comprising 

 a row of small rectangular denticles and one posteriormost distinct tooth. The 

 lateral system comprises flanges and crests. The ligament is posterior. Eyes are 

 absent. 



