MONOGUAPil OF JAPANESE OrillUnoiDEA. 389 



plates nnd seules are entirely internal and very much reduced in size ; the latter are entirely 

 proximal to the former, the two articulating with each other terminally. These features of 

 the genital plates and scales are (luite peculiar. The genital pLite has no special condyle 

 and socket for articulation with the radial shield, but the outer end itself of the plate serves 

 for an juticular facet. It may bo thought, that Aslrophlnra, is not Chilophiuridan but Tjio- 

 mophiuridau in tlie articulation of the genital plate and radial shit^ld ; Irat my view is that, this 

 condition is simply a result of the extreme reduction of the genital plates. The very l)asal 

 vertebri« are large and long, instead of being very small and short, and are quadrangular in 

 dorsal view, again reminding us of those of OphiopUnthus medusa;. The ventral side of each 

 vertebra within the pentagonal ♦' .-isteroid " body has a well marked medinn suture (fig. 2). The 

 vertebra) of the free arms are dixaded into halves by a very narrow moniliform «lit (fig. 3). The 

 articulation of the same is zygospoudylino (figs. 4 & 5), a (i^mrnon character of the OjMoimJx'mo' , 

 Opkùtcmithidœ pars, thvdhophmriäd and Chilophiurida. 



VI. V, figs. 6-12 illustrate the internal structures of tlic more typical genera of the 

 Ophiolepidkia: In all the species here illustrated, viz. Ste<ioj)hiur<i .sladeni (fig. 6), Ophioiniisium 

 trijchnum (fig. 7), 0. cnncelUdiua (fig. 8), Ophiozondld lorvfisplna (fig. 9), Ophiozoni înipi-essn (fig. 

 10), Ophioplocus japonlcus (fig. 11) and Ophlocercmis jannurü (fig. 12), the peristomial plates aro 

 doxible and small, a character common to the majority of the jiresent family ; tho double or 

 triple character of the peristomial iilatcs is common to the majority of tho Ophloh'pididœ and 

 to all the other families of th<î C'hUophiurida (all the members of tho Ophiokpididd: which are 

 atypical on this point are very padomorpbic). The teeth are slender and pointed in Stefjophmrd 

 and Ophionmsmm, show a tendency to be stout and squarish in OpftiozoneWi, are moderately 

 stout and squarish in Ophiozoiut and Ophioplocus, and very strongly so in Ophioccrdmls. The 

 stoutness of the oral frames increases also almost in the same (jrder ; the oral frames of 

 Ophiozonn and Opfiinplocus show a tendency to have lateral wings, and th(jsc of Ophioceramis 

 have well developed lateral wings. In Stegophiura, Ophlomnsium and OpUiozonelld, the first 

 vertebra is the shortest ; while i7i Ophiozom, Ophioplocus and OpJùoceramit, the second is the short- 

 est. It is noteworthy, that the very basal vertebras of Ophiomuslwn injchnum are not much 

 reduced in length ; this is a common cliaracter of the more piüdomorphic forms. 



PI. V, fig, 13 shows the internal structures of Opfdoleuri: chitrlschvnvi, a representative of 

 the Ophioleuclda: The peristomial plates aro rather large and triple; triple peristomial j)lates aro 

 also found in the Ophlodernvdlda^ l)ut not in tho Ophiolepldldd!. Tho oral ])lates and frames 

 are long and slender, and the latter do not bear well developed lateral wings ; these characters are 

 found also in the typically deep-water forms of the Ophiolcpldido;. The genital plate has two 

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

 a characteristic of the Chüophvar'uhi. The genital scales are wide, thin and leaf -like ; this character 

 is also found in <)phmr<i, and its allies, as also in the Gmithopliiuridd,, and is correlated with 

 very long genital slits. The first vertebra, not tho second, is tho shortest ; this condition is also 

 observed in (he deep-water f<:)rms of the Ophiolepvlvlfr, as well as some other families. 



