MONOGRAPH OF JAPANESE OPHIUROIDEA. 



207 



keeled along the longitudinal median line, widely in contact with 

 each other. Five arm spines, long, flattened, acute, unequal in 

 length ; the ratio of their length to the corresponding arm joint in 

 different parts of an arm may be shown approximately as follows. 



Thus, the lowest spine is always the longest and the third 

 from below the shortest ; the lowest one is longest at a certain 

 distance from the disk, being there about thrice as long as the 

 corresponding arm joint. Single, very large, oval, flat, leaf-like 

 tentacle scale to each pore. 



Colour in alcohol : whitish, except the dorsal side of the disk, 

 which is frequently light blue. 



This new species is very near to A. iris, which occurs also 

 in the Sagami Sea, but differs from it in the distinctive characters 

 already mentioned. Further, A. iridoides appears to me to differ 

 from A. glabra Lyman in the very prominent primary plates, in 

 the distinctly squamated interbrachial ventral surfaces, in the 

 much smaller and narrower oral shields, in the not very distinctly 

 separated adorai shields, in the larger, oval, flattened distal oral 

 papillae, in the longer and flattened arm spines, and in the 

 larger tentacle scales. Judging from Marktanner-Turneeetscher's 

 description, the specimen which he referrs to A. glabra appears to 

 me likely to belong to A. iridoides. 



