MONOGRAPH OF JAPANESE OPHIUROIDEA. ]85 



row of denticles, so that the disk border is serrate, quite as in 

 Clark's fig. 68d of 0. perierctus. 



Key to Japanese species of Amphipholis, 



A — Radial shields perfectly joined in pairs, 



a — Arms three to four times as long as the disk diameter; dorsal arm 

 plates distinctly shorter than the corresponding arm joint, without 

 any streak along the median line. 



h — Disk scales thin, rather indistinct from one another, so that the 

 surface of the disk is very smooth ; radial shields not very wide, 

 about two and a half times as long as wide, the united width of 

 each pair being nearly equal to the width of the corresponding arm 

 base ; three arm spines, of which the uppermost one is the longest, 

 the lowest one the shortest, and the middle one the stoutest but 



not distinctly compressed Japonica. 



hh — Disk scales thickened along the free margins, concave, very 

 distinct from one another, so that the surface of the disk is not 

 very smooth ; radial shields very wide, about twice as long as wide, 

 the united width of each pair much exceeding the width of the 

 corresponding arm base ; tliree, sometimes four, arm spines, of 

 Avhich the uppermost one is the longest, and the middle one 



the shortest and stoutest and distinctly compressed sobrina. 



CM — Ai'm seven to eight times as long as the disk diameter; dorsal arm 

 plates as long as the corresponding arm joint, with a distinct white 



streak along the median line pugetana. 



cLl — ßadial shields divergent, being nearly or entirely separated from 

 each other by a row of scales; three arm spines, of which the 

 lowest one is the longest ; adradial tentacle scale much larger than 

 the abradial Icocldi. 



