NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 213 



separated, liiterbracliial spaces below covered with (dongated sharp 

 granules, or spinelets. Genital slits large. Oral shields rounded, 

 about as long as wide, pointed proximally but with a truncate, distal 

 angle. Adoral plates somewhat variable, about three times as long 

 as wide, meeting broadly within, either wholly proximal to the oral 

 shield or else pushing down more or less between it and the first side 

 arm plate. Jaws very narrow, and compressed, each with about seven 

 long, flat, pointed oral papillae, which are subequal or the apical one 

 is largest. First under arm plate hexagonal, longer than wide, with 

 proximal margin deeply notched; succeeding plates broadly triangular 

 with lateral angles rounded and distal margin convex, much wider 

 than long; all the under arm plates are widely separated from each 

 other. Side arm plates large, meeting broadly above and below; 

 each plate carries seven slender, smooth, pointed spines, of which the 

 uppermost is longest and may exceed two joints. Tentacle scales 

 single, large, oval and flat, more or less pointed at tip. Color (dried 

 from alcohol), very pale brownish. 



Locality.— Albatross station 4781, Bering Sea, hit. 52° 14' 30" N.; 

 long. 174° 13' E., 482 fathoms, fine gray sand, pebbles, bottom tem- 

 perature 38.6°, 1 specimen. 



Type.— Cat. No. 25598, U.S.N.M., from station 4781. 



This remarkable ophiuran reminds one at once of Ophiacantha vivi- 

 para, an Antarctic species in which the females have six to eight 

 arms" although the males have only five.^ It is easily distinguished 

 by the differences in disk covering, under arm plates and oral pa- 

 piUse, but one naturally wonders whether both sexes in this north 

 Pacific' species have nine arms or whether there is here also a sexual 

 dimorphism. Other related questions naturally arise, but in the 

 presence of only a single specimen it is futile to discuss them. We 

 can only hope that further collecting in Bering Sea will bring to light 

 more abundant material of this most interesting Ophiacantha. 



OPHIACANTHA PRIONOTA, new species.'" 



Disk 9 mm. in diameter; arms about 42 mm. long. Disk covered 

 with a coarse scaling, which is only partially concealed by numerous 

 rough, stout spines, nearly a millimeter long. Distal ends of radial 

 shields visible, widely separated. Upper arm plates rhombic, ^\•ith 

 distal angle rounded, or triangular with distal margin strongly convex, 

 about as wide as long, only the first two or three in contact. Inter- 

 brachial spaces below covered with scales, upon wdiich only a few 



« Wyville Thomson (Jour. Linn. Soc. London, vol. 13, 1876, p. 77) says there are 

 six to nine arms and that he never saw fewer than six. 



6 See Koehler, ZooL Anz., voL 31, 1907, p. 229. 



c np:ov(OT6c, signifying like a saw, in reference to the character of the lowest arm 

 spines. 



