NO. 2 



rost: the family arcidae 



181 







y^' 



79 



Fig. 79. Area mutabilis (Sowerby) 1833. Puerto Parker, Costa Rica. 

 Shell with periostracum seen from the posterodorsal side. 

 Length, 20 mm. 



Fig. 80. Area mutabilis (Sowerby) 1833. Isia Isabel, Gulf of 

 California, a. Lateral view. b. Dorsal view. c. Abdominal 

 sense organs. Length, 30.8 mm. 



