NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 



87 



irregular arrangement of the disk scales may not be a species character 

 for such a condition is occasionally found as an individual variation 

 in species which normally have the disk scales very regularly disposed. 



OPHTURA BRACHYACTIS, new species, a 



Disk 17 mm. in diameter; arms about 35 mm. long. Disk high, 

 6 mm. thick, covered by a smooth, firm coat of some seventy-five 

 scales; central primary plate very small (peculiarly elongated in the 

 type, but pentagonal in the other specimen), surrounded by the five 

 very large radials, which look as though they overlapped each other 

 clockwise (probably they do not really overlap at all"). Radial shields 



FIG. 28. OPHTCJRA BRACHYACTIS. X3. a, FROM ABOVE; 6, FROM BELOW; c, SIDE VIEW op BASE OF ARM 



very large, closely joined, a trifle longer than wide; outer ends 

 slightly diverging and inner ends more or less separated by a single 

 scale. Arms high and compressed at base, but not really keeled. 

 Upper arm plates more or less hexagonal, becoming tetragonal; basal 

 ones much wider than long, distal ones somewhat longer than wide, 

 in contact throughout. Interbrachial spaces below covered by oral 

 shields and about a dozen scales. Oral shields very much longer 

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

 small and narrow, about three times as long as wide; oral plates 

 wider but not so long; an unpaired plate at tip of jaw. Oral papillae 

 small, four or five on a side, besides a terminal infradental papilla. 



o BpT.%uc, signifying short, and eucr/f, signifying ray, in reference to the short arms. 



