303 



concrete jackets at the 1st Street terry lanclint;, of which three were lounci tci he 

 attacked, one quite badly, the others containing from .^ to 6 borers each. Of 75 such 

 jackets examined by Mr. Sadler at the Kerckhoff-Cuzner Wharf, about 50 per cent 

 were found to contain borers, while about 20 per cent were quite liadh' attacked. 



Fig. 121. (1) .Sample of concrete pile-jacket containing four borers (Pholadidea penita) in a space 3 

 inches square. Two of tfie borers are visible, presence of the others being indicated by 

 openings at the lower left. 

 (2) Section through jacket showing borer holes in close proximity. One borer (Pholadidea 

 penita) in place in burrow. 

 Both natural size. 



On December 16 Dr. Miller went over this ground with Messrs. Hughes. Ludlow 

 and Sadler. A number of other jackets were broken open, and a considerable quantity 

 of specimens secured. The species occasioning most of the damage proved to be 

 Pholadidea penita Conrad, known commonly as the "rock clam." It was found from 



