172 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 23 



PLATE 17 



Polydora ivebsieri Hartman 



Lower right. Exposed valve of commercial oyster from Connecticut, 

 seen from the inner side, showing mud blisters caused by P. nuebsteri, 

 x 0.84. 



Exposed valve of the same shell, seen from the outer side, showing 

 U-shaped apertures of P. ivebsteri, x 0.84. 



Ipper left. Scallop shell, Patinopecten caurtnus (Gould) from Win- 

 chester Bay, Oregon, in 20-40 fins, attacked by P. websteri, x 0.75. 



Ipper right. Same valve as preceding, seen from the inner side, show- 

 ing mud blisters caused by P. loebsteri, x 0.75. 



Lower left. Enlarged portion of l"-shapeil burrows, near the hinge of 

 Patinopecten caurtnus, seen from the outside, x 3.5. 



