302 



Mr. Hughes reported that, of the jackets examined by him, one other was attacked 

 more heavily than this in proportion to the surface exposed; but it consisted of a ver\- 

 poor mortar, Ijadly disintegrated. 



Fig. 120 



1. Lateral and dorsal views of the rock clam, Pholadidea penita Conrad. 



2. Plaiyodon cancellata Conrad. 



3. Petricola carditoides Conrad. 



4. Large specimen of Pholadidea penita in place in burrow. 

 All specimens from Los Angeles Harbor. Natural size. 



The discovery of the borers at this locality led to the examination of other con- 

 crete jacketed piles in the harbor. Mr. J. \V. Ludlow, Harbor Engineer, stated that 

 of 12 pile jackets examined by him at the old Blinn Lumber Company wharf, opposite 

 Berth 229 in Los Angeles Harbor, three were rather badly attacked by borers. Mr. 

 W. H. Sadler, Harbor Department Chemist, reported that he had broken open 12 



