102 



autumn settling of larvae along the eastern coast of Sakhalin at temperatures 

 of 7-12°C. In Preobrazheniya Inlet (southern Primor'e), according to Adrianov 

 and Vol'ter (1947), mass metamorphosis is observed twice a year: spring 

 (March) and autumn (October-November). In southern Califomian waters, 

 Coe (1941) reported reproduction of B. setacea at temperatures of 10-15°C 

 with an additional spawning period in winter and summer. In San Francisco 

 Bay (Kofoid and Miller, 1927), the season for release of gametes begins in 

 February at a minimum temperature of lO^C and ends, for the most part, before 

 the beginning of summer, peaking in April-May. Northward, along the coast 

 of Washington (USA) and Canada, the optimum temperature for settling is that 

 in October-December, i.e., 8.0-9.5°C (Johnson and Miller, 1975). In British 

 Columbia (westem coast of Canada), this species reproduces at temperatures 

 from 12 to 15°C, with maximum larval numbers observed at depths of more 

 than 6.0 m, where the water is warmer (14-17°C) (Quayle, 1959). Thus, the 

 temperature range for reproduction of this species throughout its area of dis- 

 tribution is 8-17°C. The pelagic stage of development of 5. setacea in the 

 coastal waters of British Columbia and in southern Califomian waters (Quayle, 

 1953; Coe, 1941) continues for 20-30 days. Our observations in Busse Lagoon 

 (southern Sakhalin) established an identical period of development. 



Quayle (1953, 1955, 1959) has described the structure of larvae of B. 

 setacea. The ecology of larvae of this species has been thoroughly studied (see 

 above). 



CRISP ATE ZIRPHAEA, ZIRFAEA CRISPATA (LINNE) 



(Pholadidae) 



Veliconcha 



Initially roundish, the shell then stretches dorsoventrally, as a result of 

 which its height becomes slightly more than its length. The shoulders start to 

 slope steeply and the anterior shoulder is somewhat longer than the posterior. 

 Concentric striation is conspicuous. Before metamorphosis, a tooth on one 

 valve and a corresponding notch on the other appear on the ventral margin of 

 the shell, forming a firm lock (Figure 41 A, B). The hinge system is repre- 

 sented by two 5—10 |i,m broad teeth on the left valve, with a broad (20—25 

 jxm) tooth situated between them on the right valve; a second small tooth 

 forms at the anterior end of the right valve before metamorphosis. A ftilly 

 grown larva is 300 |i,m long, 285 |xm wide, and has a hinge line 68 |Xm in 

 length. 



