NOKTH PACIFIC OPHIURANS IN NATIONAL MUSEUM — CLARK. 



91 



resembles 0. undata Lyman in some particulars, a single glance at 

 the interbrachial areas and oral shields is sufficient to distinguish the 

 two species. From 0. solida Lyman, the arm plates alone are enough 

 to separate pomphopliora . 



OPmURA GLYPTODISCA, new species.^ 



Disk nearly 6 mm. in diameter; arms 21 mm. long. Disk tliick, 

 flat, covered by six primary plates, radial shields and two plates in 

 each interradius, but each of these plates is surrounded by smaller 

 ones, and the small plates seem to be raised above the large ones, so 

 that the surface of the disk has a little the appearance of being sculp- 

 tured. Radial shields 

 large, longer than wide, 

 closely joined. Arms 

 nearly cylindrical near 

 base and tapering to a 

 very slender tip. Upper 

 arm plates swollen, only 

 first two in contact; 

 they are more or less 

 triangular with outer 

 corners rounded, dimin- 

 ish rapidly in size, and 

 are entirely wanting 

 after about the twelfth 

 j oint . Interbrachial 



spaces below covered by 

 huge oral shields and 

 single marginal plates ; 

 at outer corners of oral 

 shields, there may be one 

 or two small plates. 

 Oral shields rounded 

 without, abruptly narrowed within, about as wide as long. Adoral 

 and oral plates well defined, the latter decidedly the larger. Oral 

 papillge seven or eight on a side, closely soldered, outermost 

 much the widest. Genital slits long; genital scales large, each 

 one wdtli a marginal series of minute papillae which become suffi- 

 ciently elongated dorsally to make a conspicuous arm comb of stout, 

 pointed teeth. First under arm plate triangular, with rounded cor- 

 ners about as long as wide; succeeding i)lates well separated from each 

 other, pentagonal quickly becoming tetragonal, with more or less 



" rXtjnrbc, signifying carved, ornamented, and dcoKoc, signifying disk, in reference to 

 the prettily ornamented appearance of the disk. 



Fig. 31.— Ophiuea glyptodisca. X8. a, from above; 6, from 



liELOW; C, SIDE VIEW OF THREE ARM JOINTS NEAR DISK. 



