92 



from the end of August to early September. Their size at this time varies from 

 300 to 380 |im. The temperature at which S. alta larvae are found in the 

 plankton ranges from 11— 22°C. Mass settling coincides with autumn cooling 

 of waters. In Vostok Bay, development of larvae occurs in the same period at 

 a similar temperature. 



Hayashi and Terai (1964) have described the morphology of larvae of this 

 species. 



RAZOR CLAM, SOLEN KRUSENSTERNI SCHRENCK 



(Solenidae) 



Veliconcha 



The description of this species is similar to that given for the family. The 

 shoulders of the larva are roundish and merge smoothly with the line of the 

 anterior and posterior margins of the shell. The maximum shell length of a 

 swimming larva is 350 fim (see Figure 49). 



Ecology 



Larvae of razor clams are found in Busse Lagoon and Vostok Bay (Peter 

 the Great Bay) at the beginning of summer (May— June). 



No data on the morphology and ecology of larvae of this species were 

 found in the literature. 



CHINESE MACTRA, MACTRA CHIENENSIS PHILIPPI 



(Mactridae) 



Veliconcha 



The maximum length of the larval shell is 260-270 \x.m. The shell is oval- 

 triangular and somewhat truncate from the posterior end. The umbones are 

 high and somewhat shifted to the posterior end. The shoulders are round and 

 high (see Figures 46 and 60). The hinge system comprises one rectangular 

 tooth on the right valve and two on the left. The ligament is situated at the 

 posterior end of the hinge line. The anterior part of the dorsal edge of the left 

 valve has one lobate tooth. The lateral teeth along the hinge resemble tubercles 

 on both valves. 



Ecology 



In Peter the Great Bay, larvae of Mactra chinensis appear in large num- 

 bers in July. Settled juveniles are found in shallow sandy open inlets well- 

 warmed by the sun. 



