The bathyal and abyssal Xylophaga (Pholadidae, Bivalvia)

The bivalve material collected by the Galathea Expedition contains 17 species of the wood boring genus Xylophaga, all of them apparently new to science. They were all obtained at depths below 400 meters. In addition to the material collected by the Galathea, four previously described species have been included in the present study: X. pvaestans E. A. Smith, X. indica E. A. Smith, X. tomlini Prashad and X. sp. mentioned by PELSNENEER (191 1). Xylophaga lives in wood and other kinds of plant debris deposited on the sea bottom; only a few species appear sometimes to live in plant material floating at the surface. During the Galathea Expedition plant remnants were obtained from altogether 56 stations between 400 and 10150m depth. This matelial was carefully examined onboard and revealed a number of specimens of Xylophaga, which were preserved in 70 % alcohol. Practica!ly all the plant material dredged during the expedition was preserved dry and subsequently examined by the present author. This resulted in a considerable number of specimens being found. Although the soft parts had already dried up prior to examination, the shells, including the accessory plates, were in most cases, in very good condition. It might seem astonishing that the Galathea collection contained such a large number of species of Xylophaga, that the number of known species is more than doubled. This is certainly not because of undue "splitting" since the specific differences found in the present material are as distinct as those found in the previously described species. It is believed that the relatively large number of new species is simply due to the special attention which, during the expedition, was paid to organisms fou~d in plant debris. No doubt future expeditions could add still more species, if the plant debris is carefully examined.