NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 79 



were either wanting or were indistinguishable. The color of most of 

 the individuals before me is some shade of brownish-yellow, but those 

 from station 3126 are nearly pure white. In these specimens also, 

 the oral shields are much narrower and more constricted than in any 

 of the others, but the differences are not sufficiently marked to raise 

 any question as to the specific identity of the form. 



OPHIURA MEGAPOMA, new species.** 



Disk 17 mm. in diameter; arms about 50 mm. long. Disk rather 

 high but flat, covered by about 100 to 150 stout, coarse plates, among 

 which the primary plates are not conspicuous. Radial shields of 

 moderate size, rather longer than broad, well separated both without 

 and within, but usually more or less in contact at the middle. Arms 

 rather high, more or less compressed near base. Upper arm plates 

 hexagonal and wider than long at base of arm, but more or less rapidly 



FIG. 23. OPHIURA MEGAPOMA. X3. O.FROMABOVE; &,FROMBELOW; c, SIDE VIEW OF THREE ARM JOINTS 



NEAR DISK. 



becoming longer than wide, and pentagonal or even tetragonal near 

 tip ; in contact except at extremity of arm. Interbrachial areas below 

 covered by about twenty rather coarse plates. Oral shields longer 

 than wide, rounded distally but pointed at inner end. Adoral plates 

 large, about twice as long as wide; oral plates smaller, much wider 

 proximally than distally ; in the type-specimen there are a number of 

 rounded granules on the inner ends of these plates, but these are 

 wanting in the other specimens. Oral papillae only three on each side, 

 rather small and somewhat pointed; they are directly continuous with 

 the tentacle scales on the outer side of the oral tentacle pore. Genital 

 slits long and moderately conspicuous. Genital scales short and wide 

 distally, rather conspicuous from above; each scale carries about eight 

 wide, truncate, crowded papillae, which, with two additional ones on 

 the outer end of each radial shield, make up the conspicuous arm 



a Me-fac, signifying big, and Tro^a, signifying lid, in reference to the large lid-like 

 tentacle scales. 



