[Introduction:]
During my stay at the Amakusa Marine Biological Station of the Kyushu Imperial University in the spring of 1935, Prof. H. Ohshima, director of the Marine Biological Station, kindly pointed out to me the existence of two polychaetes living commensally in the burrows of the apodous holothurian
Protankyra bidentata (Woodward et Barrett), found on a muddy beach at Tomioka Bay. One of the polychaetes is ascribed to a new form of
Lepidasthenia, belonging to the Polynoidae, and the other to an American species of
Podarke in the Hesionidae. No record of a similar habit commensal with the holothurian has been known in these genera.