MONOGRAPH OF JAPANESE OPHIUROIDEA. 391 



<he very basal one, being nioilerately notched at the inner eml, and that of <)plùoiie,rvis and 

 Ophiocratt'is is V shaped, being strongly notched at the inner end. The Y- or V-shape of the 

 dorsal surface of the vertebra is a common character of the Ophlotrichidœ among the Gnatlio- 

 phiurida and the Ophionereldincv, among the Chilophiuridd. 



PI. VII, figs. 4-7 illustrate the internal structures of the Ophiocom'mœ. In all the species 

 here iUustrated, viz. Ophiocoma scolopendrina (figs. 4 & 5), Ophiomastix annulosa (fig. 6) and Opjhiar- 

 thrum eleijans (fig. 7), the perLstomial plates are double and very small, as in Ophlodoris and 

 Opkionereis ; the common outline of the oral and dental j)lates is "TT-shaijed, as in Ophioceramis 

 and the Ophmiercidinw • the teeth are very stoiit and squarish .and the oral frames are very stout 

 and have well developed lateral wings, as in the Amplùuridœ, Ophlotrichidœ, Ophioceramis and 

 the OphionereidlncK ; the dorsal surface of the vertebra is rhomboidal and not strongly notched 

 at the inner end, a character distinguishing the Ophlocomimi; from the Ophionereldmœ. The 

 genital plates have, as shown in fig. 7 (Ophlarthrum elegans), each two articular condyles and 

 one articular pit to fit to the two condyles and one pit of the radial shield, a characteristic of 

 the Chllophîurîda. The genital scales are narrow and bar-like and articulate with the genital 

 Ijlates at some distance inwards from the outer ends of the latter, a common character of the 

 majority of the ChUophiurlda, viz. the Ophlomastlnœ pars, Ophlolepklinœ, Ophlodermatidœ, Ophio- 

 chitonidcr and Ophîocomidœ. The radial shields are vei-y large, subtriangular, and consist of the 

 body and a lateral wing, a character distinguishing the Ophlocomina; from the OphlopsiUnœ. 



PI. Y 11, fig. 8 shows the internal structure of OphiopsUa riisel, a representative of the Ophl- 

 opsUinœ with the sole genus OphiopsUa. The oral skeleton is throughout similar to that of the 

 Ophiocomlmv. The vertebrte are also similar, though relatively narrower. The genital plates, as 

 well as the radial shields, have each two articular condyles and one pit, and the genital scales 

 are narrow and bar-like and articulate with the genital pylates at some distance inwards from 

 the outer ends of the latter, decisive laroofs that OphiopsUa ,belongs not to the Gwiihophlurhda 

 but to the ChUophiurlda, and not to the Amphlurldœ but to the Ophîocomidœ. The outer ends 

 of the genital plates of the same radius approach more closely to each other than in the Ophiom 

 comime. The radial shields are very narrow and bar-like, the lateral wings being scarcely 

 developed, a character distinguishing OphiopsUa from all the Ophiocomlnœ. 



