MONOGEAPH OF JAPANESE OPHIUROIDEA. 295 



a — Disk convex, covered with one hundred to one hundred and fifty 



large plates elevata. 



act — Disk flat, covered with about two hundred small plates. . platydisca . 

 A A — One tentacle scale to each pore, often also with one to three small, 



supx^lementary ones on the adradial border of the pore in a few 



basal arm joints. 

 b — Disk convex ; arms long and slender, five to eight times as long as 



the disk diameter ; colour reddish or yellowish brown in alcohol. . . 



projecta. 



W>— Disk flat; arms short, tlu:ee or four times as long as the disk 



diameter ; colour white in alcohol. 

 c — Disk plates fine ; radial shields rather small, about one-third as 



long as the disk radius ; arm spines shorter than the corresponding 



arm joint polypJax. 



cc — Disk plates large ; radial shields very stout, about half as long as 



the disk radius ; arm spines of basal arm joints longer than the 



corresponding joint. longispina, 



Ophio^ouella elevata (Clark). 



Ox>Mozona elevata : Clark, Biül. Ü. S. Nat. Mus., LXXY, 1911, p. 31, 

 fig. 6. 



Off Goto Is., Eastern Sea; 95-100 fathoms (Claek). 



Ophio^onella platydisca (Clark). 



OpUozona plaUjdisca : Clark, Bull. U.S. Nat. Mus., LXXV, 1911, p 



34, fig. 7. 

 Off Hiro Misaki; 191 fathoms (Claek). 



Oj^hio^onella projecta (Kœhler). 



OpUozona j^rojecta : Kœhler, Exp. Siboga, XLV, Pt. 2, 1905, p. 19,. 

 PI. T, figs. 16-18; Clark, Bull. U. S. Nat. Mus., LXXY, 1911, p. 36. 



