2. 







Centimeters 



0,5 



Centimeter 



Figure 394. — O. (Trilonalia) japonica Dunker, Japanese species from oyster bottom of Piiget Sound, Wash. 1 — apertural 



view; 2 — abapertural view; 3 — egg case. 



Figure 395. — Edge of the shell of an oyster killed by 

 Busycon in Oyster River, Chatham, Mass. Straight 

 line at the lower edge of the shell indicates the place of 

 rasping by the conch's radula after the valves were 

 chipped. 



cycles. In Cape Cod estuaries, egg cases of conclis 

 are a familiar sight on tidal flats at low water 

 (fig. 396). Under experimental conditions the 

 conchs were found to consume in summer about 

 three adult oysters per week (Carriker, 1951). 



Small parasitizing pyramilid snails of the genus 

 Odostomia {Meneslho) congi'egate in large numbers 

 at the very edge of oyster shells. \Vhen the 

 valves are open, the snails extend their pro- 



FiGURE 396. — B. carica depositing egg capsules at low 

 Tide. Woods Hole. 



436 



FISH AND WILDLIFE SERVICE 



