MONOGEArH OF JAPANESE OrHIUROIDEA. 181 



in contact with each other. Oral plates long and narrow. Six 

 oral papilla} on either side, flat, obtuse, except the outermost one, 

 which has pointed inner end. Teeth quadrangular, stout, with 

 truncate free end. 



Six arms, of which three are longer and stouter than the 

 others. Dorsal arm plates hexagonal, with rounded outer angles, 

 slightly longer than wide, widest at the lateral angles, in contact 

 with each other. Lateral arm plates low, those of the two sides 

 not meeting above or below. First ventral arm plate very small, 

 pentagonal, longer than wide. Those beyond hexagonal, with 

 concave lateral and notched outer borders and rounded outer 

 angles, slightly longer than wide, widest at the outer angles. 

 Four arm spines in the free basal joints, cylindrical, tapered, 

 blunt ; the second from above which is the longest, is slightly 

 longer than the corresponding arm joint, while the lewdest one, 

 which is the shortest, is slightly shorter than the same. A short 

 distance out from the disk, there are only three arm spines on 

 either side of each arm joint, the uppermost being ^the longest. 

 A single large, oval, flat tentacle scale to each pore, except the 

 first v>rhich has usually two scales. 



Colour in alcohol bluish. 



This new species very much resembles A. sexracUa (Duncan, 

 1889), but differs from it in the fewer and more widely spaced 

 disk spines, in the quite distinct disk scales and radial shields, in 

 the more numerous oral papilla3, in the longer and narrower oral 

 shields, in the shape of the dorsal and ventral arm plates and in 

 tlie longer arm spines. 



