THREE NEW SPECIES OF THE GENUS PSEUDOSTICHOPUS FROM THE JAPANESE WATERS1l

ln examining the holothurians collected on October 27, 1976 from the 400-450 m deep floor around Shimo-Koshiki Island off the west coast of Kyushu Island, there were found two species of the genus Pseudostichopus Theel, 1876, that were clearly different from any of six species of this genus so far known from the Japanese Waters. In addition, five specimens of another form collected in 1972-73 from the 200-300 m floor off the coast of Akita Prefecture in the Japan Sea were sub-mitted to the present auther by Dr. Saburo Nishimura for identification. These species were compared carefully with 13 species of Pseudostichopus so far described. Then, it was found that they were seemingly distinct from any known species but representing new ones respectively. Generally in the species of this genus, however, the ambulacral appendages are so small that it is rather difficult to identify the pedicels and the papillae distinctively and to show correctly their arrangement and distribution. Further, the ossicles in various parts of holothurians will differ considerably in appearance and density with their growth and probably with some other factors. Therefore, the decisive identification might be better suspended till an eonugh number of specimens, showing the range of variation in respective aspects, are secured. On the other hand, from a practical point of view to promote the studies in the bathyal holothurians that are found only scarcely in the catches by trawl or dredge, it is urged to record them exactly. The present three species of Pseudostichopus from Japan are described below for this reason rather tentatively. The position of this genus is based on Svend Reding ( 1940). The auther wishes to express his hearty thanks to Dr. Takasi Tokioka and Dr. Suguru Ohta for reading the manuscript, also to Dr. S. Nishimura for important specimens