ÄIONOGRAPH OF JAPANESE OPHIUROIDEA. 13 



vertebrae entire, except in very distal arm joints ; arm spines not 

 converted into compound hooks, except in the very distal arm 

 joints Ophiomyœa. 



dd — Marginal disk scales absent. 

 f- — Radial shields present ; dorsal arm plates usually absent (or some- 

 times present, being divided into several secondary plates, as in 

 the Japanese species) ; arm spines free from each other. . OpModera. 



ff — Radial sliields absent ; dorsal arm plates entirely wanting ; arm 

 spines connected together by a web-like membrane .... OpMohyTnen. 



OpJiiosy^ygns disacanthus Clark. 



OpMosyzygus disacanthus : Clark, Bull. U. S. Nat. Mus., LXXV, 1911, 

 p. 276, fig. 139. 



Off Kagosliima Gulf; 103-152 fathoms (Claek). Uraga Chan- 

 nel ; 88 fathoms (Clakk). 



Ophioleptoplax megaxyora Clark. 



Op7iioIepfo2:)lax megapora : Ctj^rk, Bull. U. S. Nat. Mus., LXXV, 1911, 

 p. 279, fig. 141. 



Eastern Sea; 71 fathoms (Clark). 



Ophiostyraciuni tvachyacanthiini Clark. 



OpMosfyracivm trachyacanthum : Clark, Bull. U. S. Nat. Mus., LXXV, 

 1911, p. 253, fig. 124. 



Eastern Sea ; 440 fathoms (Claek). 



Ophiostiba Matsumoto, 1915. 



Disk and arras covered by a soft, thin skin, which contains 

 some granules in the former. Marginal disk scales present. Radial 

 shields very rudimentary, forming a continuous row with the 

 marginal disk scales. Teeth and oral papillae present, triangular, 



