NORTH PACIFIC OPHlURANS IN NATIONAL MUSEUM CLARK. 26? 



specimens of it were taken by the Fisheries steamer Albatross on either 

 of her Japanese cruises. 



OPHIOTHRIX MACROBRACHIA, new species, a 



Disk 11 mm. in diameter; arms apparently about 165 mm. long. 

 Disk covered with a thick skin containing scales which bear slender, 

 minutely thorny spines of variable length and acuteness. Radial 

 shields very large, but completely hidden by the skin, except at inner 

 distal corner, where they are barely in contact. Upper arm plates 

 pentagonal, becoming squarish far out on arm; first four or five small 

 and separated from each other by skin; succeeding twenty or so in 

 contact ; remainder more or less separated. Interbrachial spaces below 



FIG. 133. OPHIOTHRIX MACROBRACHIA. X 4.5. a, FROM ABOVE; 6, FROM BELOW; c, SIDE VIEW OF TWO 



ARM JOINTS NEAR DISK. 



quite naked, the thin skin with only a few scattered minute spine- 

 lets. Oral shields wide, sometimes twice as wide as long, more or less 

 oval or elliptical. Adoral plates very small, not meeting within; jaw 

 frames with a large median perforation. Teeth about four and teeth 

 papillae about twenty on each jaw. Under arm plates with rather 

 indistinct outlines, but hardly in contact with each other, and usually 

 well separated; first two or three longer than wide, following squarish 

 or wider than long until toward tip of arm, they become longer than 

 wide again; each plate has a more or less distinct median, minute 

 notch in distal and proximal margins, connected by a longitudinal line 

 on its surface, the cause of which is hard to determine, for it is not 



a MoKpoe, signifying long, and ftpa%'ctov, signifying arm, in reference to the very long 

 arms. 



