the period covered by the tests, but the attack usually did not exceed 

 a trace. In Test Board No. 1, maxlmiam attacks rated slight In 1946 and , 

 19^7; but In Test Board No. 2, only mere traces vere recorded. Pholadldae 

 also occurred at this location, the attack rating slight in Test Board 

 No. 1 and practically a mere trace in Test Board No. 2. 



b. Foxaing Organisms . Silt, algae, and invertebrate a n i m als 

 belonging to 8 phyla contributed to fouling of the panels. The latter 

 comprised sponges, hydrolds, encrusting and filamentous Bryozoa, 

 brachlopods, marine vorms, barnacles, miscellaneous nonborlng mollusks, 

 and tunica tes. Hydrolds and encrusting and filamentous Bj^^ozoa occurred 

 most frequently, barnacles somewhat less frequently, while the occurrence 

 of the others was purely sporadic or occasional. Algae occurred as traces 

 on two test panels of Test Board No. 1. 



5. Eecent Addenda . Test Board No. 1 showed a very heavy attack 

 from sets of Teredinldae in 19^8 and 19^9. ^e attack by Limnorla was 

 slight in each of these yeeirs. Pholads (Hiata and Martesia ) were medium 

 heavy in 19kQ, but their attack in 19i^9 rated only slight. A test 

 board installed at the Navy Pier No. 2 on June 5, 19^* showed a trace 

 of Teredinldae from the set of I9W and a moderate attack from the 

 set of 19it9. There was a trace of Limnorla on the panels of this board 

 each year. Pholads ( Hiata and tfertesia ) were moderate here in both years. 



218 



