ECHINODERMS (OTHER THAN HOLOTHURIANS) 



COLLECTED ON THE PRESIDENTIAL 



CRUISE OF 1938 



By AUSTIN H. CLARK 

 Curator, Division of Echinodcrms, U. S. National Museum 



(With Five Plates) 



During the cruise of the U.S.S. Houston with President Roosevelt 

 on board in the summer of 1938 Dr. Waldo L. Schmitt, who partici- 

 pated in the expedition as Naturalist, obtained specimens of 23 species 

 of echinoderms other than holothurians. Although small, this collec- 

 tion is remarkable in including three new species, as well as repre- 

 sentatives of several very rare species. 



From Clipperton Island come numerous specimens of a curious 

 small ophiuran that appears to be identical with one described from 

 Mer in the Murray Islands, Torres Strait, by Dr. Hubert Lyman 

 Clark in 191 5 under the name of Ophiocoma parva. In 1921 Dr. Clark 

 compared Ophiocoma parva with the 6-armed young of the West 

 Indian O. pumila, which it very closely resembles. He said it seems 

 probable that 0. parva is the young of a larger 5-armed species. 



The discovery of O. parva on Clipperton Island, where, as in Torres 

 Strait, no species related to O. pumila is known to occur, led to an 

 examination of the relationships between O. parva, and a related 

 species from the Galapagos Islands, with O. pumila. 



It was found that these species are closely related to the 6-armed 

 individuals assumed to be the young of O. pumila. But these 6-armed 

 individuals show such marked differences from 5-armed O. pumila 

 of approximately the same size that they certainly cannot represent 

 the same species. 



I have, therefore, segregated Ophiocoma parva, the related species 

 from the Galapagos Islands, and the related species from the West 

 Indies hitherto assumed to be the 6-armed young of O. pumila, in the 

 new genus Ophiocomella, a genus closely allied to, though apparently 

 quite distinct from, Ophiocoma. 



Smithsonian Miscellaneous Collections, Vol. 98, No. 11 



