MONOGEAPH OF J.\PANESE OPHIUEOIDEA. 115 



leaving a long, narrow, naked space. First ventral arm plate 

 small, hexagonal, with concave inner side, about as wide as 

 long. The second is the largest, and is triangular, with truncated 

 inner angle and curved outer border, a little wider than long, in 

 contact with the first plate. The rest are triangular, with acute 

 inner angle and curved outer border, wider than long, separated 

 from each other by the lateral arm plates. The outer border of 

 the ventral plates consists indistinctly of three portions, of which 

 the median is very slightly concave. Five or six arm spines, 

 long, slender, spiniform, terete, solid, entire, except the lower 

 spines, which are slightly thorny at the tips. The upper spines 

 are longer than the lower. The uppermost one is about twice as 

 long as, and the lowest a little shorter than, the corresponding 

 arm joint. The lower spines are crowded and lie flat on the 

 ventral surface of the arms. One tentacle scale, very minute» 

 acutely pointed. 



Colour in alcohol : disk light yellowish gray, arms light 

 yellow. 



This species is very near to 0. frachijbaclra Claek, 1911, but 

 differs from it cliiefly in the fewer disk tubercles, in the fewer 

 oral papillae, in the shape of the oral shields and ventral arm 

 plates, and in the fewer arm spines, which are never club-shaped. 



Like 0. trachybadra, this species has some external re- 

 semblances to Ophiolehes. However, I believe with Claek, that it 

 is more natural to plat3e it in Ophlacantha than in Ophiolehes. 



Ophiacantha levispina Lyman. 



Opiiiacantha levispina : Lyman, Bull. Mus. Comp. Zool., V, 1878, p. 147, 

 PI. X, fig. 277 ; Lyman, Rep. Challenger, V, 1882, p. 196, PI. XXV, figs. 

 1-3; Clark, BuU. U. S. Nat. Mus., LXXV, 1911, p. 198. 



