The Xylophagainae are marine wood-boring bivalves which are largely confined to depths greater than 150 meters. They are not found in the intertidal zone, occur in the sublittoral only in higher latitudes, and are the sole wood-borers in depths over 200 meters. The greatest known depth for the invasion of test wood by Teredinidae is 200 meters (Tipper, 1968). The known depth range for the Xylophagainae extends from two meters below low tide in Millport, Scotland, to 7290 meters in the Banda Trench, off Ceram. Only occasionally are they found in drift wood, and this is usually after storms, the water logged wood having been lifted off the bottom and carried ashore by strong waves. The discovery of the new genus and species described here is the result of a world-wide study of the Xylophagainae, a subfamily of the Pholadidae characterized by teredinid-like shells and a small, divided mesoplax. They lack apophyses (as do the Jouannetiinae) and do not produce a callum in the adult stage (as in the Pholadinae). They are unique among the Pholadidae in having a woodstoring caecum.