298 



dorsal and ventral margins of the valves, and a large emarginated dorsal shield 

 covering the umbonal region. 



This species has occurred occasionally in the test blocks sent in from Pearl 

 Harbor, rarely more than three or four small specimens of a maximum length of 

 2 cm. occurring in any one block. That the organism is of economic importance in 

 this region, however, is indicated in the photograph, figure 118, showing Alarlesia to 

 have burrowed through 1" redwood sheathing and a layer of tarred ship's felt within, 

 during a period of 20 months' exposure in Pearl Harbor. Damage by Martesia striata 

 and Teredo diegensis in a 12" x 12" timber exposed 10 months in Pearl Harbor is 

 shown in figure 119. Reports from the Gulf of Mexico indicate that Martesia bores 

 very effectively in creosoted timbers; but we are informed by Commander C. A. 

 Carlson, Public Works Officer, U. S. Naval Station, Hawaii, that no evidence has 

 been found of damage to creosoted piling in Pearl Harbor by this borer. 



Burrows attributed to this organism were found in one of the test blocks sent in 

 from Nawiliwili Bay, although the animals themselves had been lost out before the 

 block was sent in, thus precluding certain identification. 



At Cavite, Philippine Islands, attack by Martesia on the test blocks was rapid 

 and extremely destructive (fig. 117), the damage occasioned by Teredo at this 

 locality, although considerable, being secondary to that occasioned by Martesia. 

 Blocks exposed four months or longer were usually in a crumbling condition, the sur- 

 face being riddled by small Martesia, mostly less than 2 cm. in length. 



A species of Martesia of uncertain identity occurred in some of the test blocks 

 sent in from Mazatlan, Mexico. It did not appear at Topolobampo nor Guaymas 

 nor in any harbors along the Pacific Coast farther north. 



Othkr Species 



Bankia mexicana has occurred in test blocks sent in from Mazatlan and Topolo- 

 bampo, the former at the entrance to the Gulf of California, the latter a little farther 

 north along the Gulf. The board at Mazatlan was installed August 20, 1922, and 

 showed attack by Bankia mexicana in less than a month. Growth was very rapid, a 

 length of 15 cm. being attained by the end of October. By the following April the 

 blocks were entirely riddled and in a crumbling condition. A new board was placed 

 here on May 1, 1923. Attack on this board commenced in June, and increased through 

 the summer. The board at Topolobampo was placed February 1, 1923. Initial attack 

 by Bankia mexicana appeared on the third block, removed March 16, but growth of 

 the organism was much retarded until after May 1. Specimens 25 cm. long were 

 found by the end of July, and by August IS the blocks were thoroughly riddled. 



The temperature relations of this species accordingly appear to be quite different 

 from those of Bankia setacea, conditions for the growth and reproduction of Bankia 

 mexicana being most favorable during the warmer months of the year. 



Of the biology of Bankia excolpa and Bankia orciitti nothing is known, except 

 that some specimens have been taken in the past in the Gulf of California. Neither 

 of these species has come to light in our investigations. 



Teredo parksi appears to be the dominant species in the Pacific Islands, being 

 present at all localities in the Islands from which test blocks were received, except 

 Nawiliwili, Kauai. The heaviest attack by this species occurred in Pearl Harbor. 

 Blocks submerged here September 1 showed considerable surface attack at the end 

 of a month, and by the end of the second month a length of 8 cm. had been attained 

 by the largest specimens. At the end of five months the blocks were thoroughly 

 honeycombed and beginning to crumble as a result of the combined attack of Teredo 



