MONOGRArH OF JAPANESE OPHIUROIDEA. 99 



rudimentary, being represented merely by the creases between the 



interbrachial ventral surfaces and arm bases. . , Ophiothamnns . 



nn — Disk not distinctly five-lobed ; radial shields joined in pairs nearly 

 along the entire length ; oral shields large, joined with the first lateral 

 arm plates ; each interbrachial ventral surface covered chiefly with two or 

 three very large scales ; genital bursœ well developed . . OpMui'othamnus. 

 mm — Outermost oral papilla not especially large; arras not very knotted; 

 arm spines of both sides never approximating dorsally ; dorsal arm 

 -. plates rather large, in contact with each other at least in proximal 

 arm joints ; disk distinctly five-lobed ; special marginal disk scales 



well developed OpJdoplinfhaca . 



11 — Numerous oral papilla not in a single series, but clustered along 



the sides and at the top of each jaw, or at least on both sides of 



the outer end of each oral slit. 



o — Disk distinctly five-lobed ; special marginal disk scales well 



developed ; radial shields separated from each other ; single tentacle 



scale to each pore OpMomilra. 



00 — Disk not distinctly five-lobed ; special marginal disk scales absent ; 

 radial shields joined in pairs along the entire length ; usually three 

 tentacle scales forming a tube for the ventrally turned up 



tentacle OpMocamax. 



ee — Arm plates and arm spines covered over by a cereous skin. 



p — Radial shields long, narrow, bar -like Ophidlebes. 



pp — Radial shields short, rounded or triangular OpJdosemnotes. 



Ophioniyces spathifer Lyman. 



OpUoimjces spathifer : Lyman, Bull. Mus. Comp. Zool., YI, Pt. 2, 1879, 

 p. 47, PI. XIV, figs. 386-388 ; Lyman, Piep. Challenger, V, p. 240, PI. XIX, 

 figs. 10-12. 



YensM Sea ; 565 fathoms (Ly^ian). 



Ophiologimus hexactls Clark 



Ophiologlmus liexactis : Clark, Bull. U. 8. Nat. Mus., LXXV, 1911, p. 

 252, fig. 123. 



