NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 223 



OPHIACANTHA EURYPOMA, new species.a 



Disk 15 mm. in diameter; arms about 85 mm. long. Disk covered 

 with very minute thorny stumps, which are more or less rubbed off, 

 leaving the underlying scaling bare. Radial shields roundish, bare, 

 near together, and sometimes almost touching distally. Upper arm 

 plates triangular, about as wide as long, well separated, except two 

 at base of arm, which are tetragonal and broadly in contact. Inter- 

 brachial" space below, like disk. Genital slits small. Oral shield 

 rhombic, with rounded angles, witler than long. Adoral plates large, 

 only about twice as long as wide, meeting broadly within. Oral 

 papillae three on a side and one at apex of jaw; all are long and con- 



FIG. 103. OPHIACANTHA EURYPOMA. x 3.5. a, FROM ABOVE; 6, FROM BELOW; c, SIDE VIEW OF TWO 



ARM JOINTS NEAR DISK. 



spicuous, and all but the outermost arc narrow and sharp; outermost 

 very wide, squarish. First under arm plate hexagonal, wider than 

 long; second plate, in contact with first, broadly bell-shaped, much 

 wider than long; succeeding plates heptagonal, hexagonal or tetrag- 

 onal, at first wider than long, but becoming longer than wide, sepa- 

 rated from each other. Side arm plates moderate, meeting slightly 

 above and below; each plate carries seven or eight slender spines, the 

 upper ones smooth, the lower ones very slightly thorny, the lowest 



, signifying lid, in reference to the broad, distal 



uf, signifying broad, and 

 oral papilla. 



