390 ART. 2. — H. MATSUMOTO : 



PI. VI, figs. 1-7 illustrate the internal structures of the OphiodermatiJa: In all the species 

 here illustrated, viz. Ophiurodon r/rmidisquama (fig. 1), Ophiurochœta mixta (fig. 2), Ophiuroconis 

 miliaria (fig. 3), Ophiarachna incrassaia (fig. 4). Bnthypedinura i/otoi (fig. 5). Fectinura anchysta 

 (fig. 6) and Ophiaraclüwlla gorgonia (fig. 7), the peristomial plates are moderately large and 

 triple, a common character of the Ophîodermatidœ and Ophiochitoninœ as well as OpMoleuce and 

 Ophiocrasis ; the oral frames do not have well developed lateral wings, a common character of 

 the Ophiolepidvdœ pars, Opihioleuddce, Ophîodermatidœ and Ophiochitoninœ, in contrast to the 

 Ophionereidinœ, Ophiocomidœ and Ophioceramis ; the teeth are not very stout, though often 

 squarish. That Ophiurodon, Ophiurochœta and Ophiuroconis have triple peristomi.al plates is a 

 proof of their being Ophiodermatine and not Ophiacanthine. The majority of the Ophiacanthida; 

 h.ave almost entire peristomial plates, and Ophiothamnus, the only known Ophiacanthine 

 member with triple peristomial plates, is very different from the genera in question. The oral 

 frames of Ophiarachna incrassaia (fig. 4) and Baihypectimira gotoi (fig. 5) are especially long 

 and have V-shaped grooves for the ambulacral ring-canal, much reminding us of those of 

 Ophiochiton fastigatus (fig. 8). 



PI. VI, figs. 8 & 9 illiLstrate the internal structures of the Ophiochitoninœ, which are almost 

 similar to those of the Ophiodermatidœ. In both the species here illustrated, viz. Ophiochiton 

 fastigatus (fig. 8) and Ophioplax lamellosa (fig. 9), the peristomial plates are moderately large 

 and triple, quite as in the Ophiodermatidœ ; the oral frames do not have well developed lateral 

 wings, and the teeth are not very stout, again as in the Ophiodermatidcü and certain other 

 families ; and the dorsal surface of the vertebra is rhomboidal, instead of being strongly 

 notched at the inner end, qiüte as in many other families, but not as in tbe Ophionereidina'. The 

 oral frames of Opjhiochiton fastijatus are es]3ecially long and have V-sbaped grooves for the 

 ambulacral ring-canal, like those of Ophiarachna incrassaia and BathypeetiMura gotoi, as already 

 mentioned. The genital plate of Ophiochiton fastigatus has two articular condyles and one 

 articul.ar pit to fit to the two condyles and one pit of the radial shield, a characteristic of the 

 ChUop)hlurid<i. 



PI. VI, figs. 10 & 11 .ind PI. VII, figs. 1-3 illustrate the internal structures of the 

 Ophionereidbur. The peristomial plates of Ophiodoris pericalles (PI. VI, fig. lOj, Ophionereis 

 annulula (PI. VIT, fig. 1) and 0. reticulata (PI. VII, fig. 2) are double and very small, quite as 

 in the Opjhiocomidœ, and those of Ophiocrasis marktanneri (PL VII, fig. 3) are triple and very 

 small. The common outline of the oral and dental plates of all the species here illiustrated i* 

 TT-shaped instead of being X-shajjed, a common character of Ophioceramis, the OpMonereldinœ 

 and Ophiocomidœ among the Chilophvurida, in striking contrast to the Amphiuridœ and 

 Ophiotricltidœ' among the Gnatfiophiurida. The teeth of all the Ophio'tiereidina; are stout and 

 squarish, quite as in Ophioceramis, Ophiocomidœ, Amp)hiuridœ and Ophiotrichidcc. The oral 

 frames of Ophiodoris are moderately stout and have more or less well developed lateral wings, 

 and those of Ophionereis and Ophiocrasis are very stout and have very well developed lateral 

 wings. The dorsal surface .of the vertebra of OpJdodoris (PI. VI, fig, 11) is Y-shaped, except in 



