PROCEEDINGS OF THE UNITED STATES NATIONAL MUSEUM 



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SMITHSONIAN INSTITUTION 



U. S. NATIONAL MUSEUM 



Vol. 90 W,.hin«ton : 1941 No. 31 14 



A NEW GENUS OF SEA STARS (PLAZASTER) FROM JAPAN, 

 WITH A NOTE ON THE GENUS PARASTERINA 



By Walter K. Fisher 



De. Tohru Uchida (1928) described a new sea star from Mutsu Bay, 

 Honshu, as Labidiaster borealis, which appeared to refute the behef 

 that the highly speciahzed Labidiaster is confined to Antarctic and 

 sub-Antarctic regions. Of this genus, described by Liitken (1871, 

 p. 289), there are two species: L. radiosus Liitken (synonym L. crassus 

 Koehler), distributed over the Falkland Plateau and off the southern 

 end of South America, 0-183 m.; and L. annulatus Sladen (1889, p. 

 595, pi. 108, fig. 1), an Antarctic species found at Kerguelen and 

 Heard Islands, Antarctic Archipelago, South Orkneys, South Sand- 

 wich Islands, and South Georgia, 93-44 m. 



Through the kindness of Dr. R. Hayashi, Department of Zoology, 

 Hokkaido Imperial University, Sapporo, Japan, I have received two 

 dried specimens of Labidiaster borealis Uchida from Hokkaido. One 

 of these is larger than any recorded by Dr. Uchida, R bemg about 180 

 mm. and r 30 mm. The specimen had 35 rays of which 10 remain. 



This species is not a Labidiaster, nor does it appear to be closely 

 enough allied to be included in the Labidiasterinae. The various 

 polybrachiate genera of Asteriidae are not very closely related, for the 

 development of numerous rays seems to have arisen independently 

 in all sorts of places. We have such divergent genera, for instance, as 

 Heliaster (usually accorded family rank), Pycnopodia, Coronaster, 

 Rathbunaster, Labidiaster, and Saliasterias. I have recently described 

 a rather anomalous sub-Antarctic genus, Psalidaster, distantly allied 

 to Notasterias; and the condition in a more restrained form exists in 



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