Plate 18 



Fig. 1. Zirfaea gahhi Tryon ; Piddock. Crescent City. One-half natural size. 

 Exterior of right valve. The siphon is partially extended but is incomplete 

 and the tip has been bent in preserving. 



Fig. 2. Panope generosa Gould ; Geoduck. Morro Bay. One-half natural size. 

 Exterior of right valve with partially extended siphon. In life the mantle 

 sliows beyond the shell margin at all points. 



