MONOGKAPH OF JAPANESE OPHIUROIDEA. 237 



halves being very slender and lying very closely side by side. 

 The articulation of the vertebra' is primitive and zygospondyline. 

 The articular peg is situated between the halves of the articular 

 shoulder, the three being almost parallel. In the inner articular 

 face, there is present a well developed articular umbo, the articular 

 knobs being, however, very rudimentary, represented merely by 

 the projecting edges of the central ridge, on which the articular 

 umbo and the pit for the articular peg are placed. Astrophiura 

 appears to remind us more or less of OphiopUnthus meclusœ Lyiian, 

 the internal structures of which have been described and figured 

 by Lyman, by its long oral frames, the absence of distinct 

 peristomial plates and the quadrangular dorsal side of the basal 

 vertebrcT. 



According to Lyman, OpJuomasfus secundus Lyman has very 

 long oral frames and plates, a small, simple peristomial plate in 

 each interradius and quadrangular, not discoidial, basal vertebrae. 

 I suppose that, the internal structures of Ophiophycis, Ophiomisidium 

 and Ophlotypa are probably similar to those of such genera as 

 Astrophiura, OphiopUnthus and Ophiomastus, though they have not 

 been thoroughly studied. Haplophiura gymnopora (Clark) has also 

 simple, transversely bar-like peristomial plates and short, discoidal 

 basal vertebra?. This genus, as well as Ophiomisidium, Ophiophycis 

 and Astrophiura, lacks the genital bursa? and visible genital slits. 

 Ophiocten sericeum Lyiian is described by the author to have also 

 simple peristomial plates and short, discoidal basal vertebra?. 



Stegophiura sladeni (Duncan), as well as St. sterea (Claek), 

 has double, transversely bar-like peristomial plates and very high 

 outer ends of the oral frames. The internal structures of Ophiura 

 kinbergi are almost similar to those of Stegophiura except the oral 

 frames, of which the outer ends are not very high. Ophiura 



