NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 



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 pompJiophora. 



OPHIURA GLYPTODISCA, new species." 



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



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 



joint. 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. Ador'al 



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



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



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



one with 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 plates well separated from each 



other, pentagonal quickly becoming tetragonal, with more or less 



FIG. 31. OPHIURA GLYPTODISCA. X8. a, FROM ABOVE; 6, FROM 

 BELOW; c, SIDE VIEW OF THREE ARM JOINTS NEAR IHSK. 



f, signifying carved, ornamented, and dianof, signifying disk, in reference to 

 the prettily ornamented appearance of the disk. 



