y^ 



5 . Pholadldae (Hlata and Martesla ) . Pholadldae also vere more 

 6r less active throughout much of the period covered by the test. They 

 occurred in 7 of the ^1 control panels hut were only eaibryonic or 

 minute except in one panel, inadvertently left submerged for 2 months, 

 where lengths up to 10 mm were recorded. One of these panels was re- 

 corded as containing 95 to 100 minute Teredinidae and Pholadidae 

 per sq. in., 6,600 in aJ.1. In the test panels, Pholadidae occurred 

 in Ik of the k7f the greatest length recorded being 12 mm after 5 

 months' submergence. The largest number recorded in any one of these 

 panels was 75 to 100, these rangitig \ip to 4 mm in diameter after 2 

 months' submergence. However, k panels were more or less conpletely 

 destroyed, presumably by the combined attacks of Teredinidae and 

 Pholadidae , so that it was in5)ossible to make exact counts of the 

 numbers of either of these organisms. The occurrence of the Pholads was 

 iiregular and sporadic in both the control and test panels. They were 

 recorded in only one test psmel from Atagust 11, 19^5 to July 20, 19^7* 

 but 7 of these panels were destroyed and could not be read. In a few 

 of the psmels vlaere Pholads were recorded, it was difficult to evaluate 

 their number and in^jortance . The Pholad attaxjk appears to have rated 

 medium heavy in 19^^ and 19i<-7, and moderate in 19^5 and 19^6. It 

 probably would have been heavier had it not been for the rapidity with 

 which the Teredinidae destroyed "Qie panels. 



A17.04 Fouling Agents 



1. Silt . Silt occurred on all except one of the hi control 

 panels and on kO of the ^7 test panels. So little was left of the 

 other, 7 panels that it was in^ossible to identify silt, or much 

 else in the way of fouling organisms. The deposits ranged usueuLly 

 from traces to moderate on the panels of both series, becoming heavier 

 after the middle of 19*^6. 



2. Invertebrate animal phyla . 



a. Coelenterata (hydroids ) . Hydroids occurred on 27 of 

 the hi control panels and on 35 of the ^7 test panels. The growths 

 rated mostly as traces on the control pemels, and as traces or light 

 on the test panels. Tubularia was the only fonn identified. 



b . Bryozoa (encrusting and filamentous ) . Encrusting 

 Bryozoa occurred more or less abundantly on 15 of the kl control 

 panels and on 22 of the 47 test panels. Two control panels were 

 covered; and of 6 of the test panels, k were 25^, 50^> 50^> and 



90^ covered, and 2 entirely covered. Cryptosula pallasiana , Electra 

 sp., and Schizoporella unicornis were identified. Filamentous Bryozoa • 



82 



