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CHAPTER XIII 



THE CLASSIFICATION OF THE SHIPWORMS OF THE 

 PACIFIC COAST AND ISLANDS 



The earliest scientific account of the occurrence of marine borers on the Pacific 

 Coast appears to be Tryon's description of Xylotrya (now Bankia) seiacea from San 

 Francisco Bay in 1863, in which account it is stated that this species had occasioned 

 considerable damage here several years previously, but "appears since to have become 

 rare." This rarity, however, unfortunately, did not persist, and in the report of the 

 California Board of State Harbor Commissioners for 1871, at which time it was current 

 practice to use untreated piles with the bark on, it is stated that the ravages of the 

 shipworm necessitated the renewal of the piling every three or four years, if not more 

 often. There is in the Museum of the Academy of Natural Sciences, Philadelphia, a 

 specimen of piling taken from San Francisco Bay in May, 1867, which shows the 

 characteristic burrows of Bankia setacea. It seems likely that this species is indigenous 

 to the Pacific Coast, its discovery being incident upon the sudden increase of shipping 

 following the gold rush of 1849. 



No other species of shipworm was reported from this Coast until 1916, when 

 Teredo diegensis was described by Bartsch from San Diego Bay. Shortly afterwards a 

 shipworm was reported by Barrows (1917) from the upper reaches of San Francisco 

 Bay, which was first identified by Bartsch as T. dieaensis, but later shown by Kofoid 

 (1921) and others to be identical with the well known Teredo navalis of European 

 waters. Teredo diegensis was, however, found by Kofoid at this time at one locality 

 in San Francisco Bay, namely South San Francisco, thus bringing the number of 

 molluscan borers known to occur in the bay to three. 



It is practically certain that Teredo navalis has been imported to San Francisco 

 Bay within recent years, probably between 1910 and 1912. The first damage by it 

 was noticed in the Mare Island dykes in January, 1914, although Barrows (1917) 

 considers that an initial infection may have occurred as early as the summer of 1911. 



The history of Teredo diegensis on this coast is more obscure. This species has 

 been found at one locality in the Hawaiian Islands, and it undoubtedly has occurred 

 in San Diego Bay for a number of years, as Dr. Bartsch states that the specimens on 

 which his description is based were collected by Hemphill, at some time prior to 1896. 

 But whether it was introduced to this coast from the Islands, or to the Islands from 

 this coast, it is not at present possible to say. 



The facility with which the shipworms may be carried from place to place and 

 introduced to new localities through the unwitting assistance of oceanic commerce 

 renders the problems of their geographic distribution peculiarly complex; and in most 

 cases the history of any species in this regard cannot be traced with even a remote 

 approach to adequacy. 



For the same reason the classification of the Teredinidae is fraught with peculiar 

 difficulties. The adaptability of the shipworms to so wide a range of conditions, and 

 the fact that the same species may be transported from place to place in shipping and 

 so occur in widely separated portions of the world, inevitably results in numerous 

 locality variates. It is difficult, often impossible, to tell whether apparent local races 

 found are generically distinct, or merely represent the immediate impress of the 

 environment on the individual specimens. Furthermore, the shell, which among 



