MONOGRAPH OF JAPANESE OPHIUROIDEA. 387 



of the Opldodennntkht; being always triple and rather long relatively to their width. The oral 

 frames of Ophiolimni are very slender, a character of those forms of the Ophincinthidcr with 

 zygospondyline vertebral articnlation ; those of Ophlolehes and Ophiaamtfui. hidentata are rather 

 stout, a character of those forms of the same family with streptospondyline vertebral articula- 

 tion. The vertebral articulation of the latter type is illustrated here by Ophiacantha hidentata 

 (tigs. 2 A' 3). It is noteworthy that both the types of vertebral articulation are represented in 

 Ophwcardha ; Ophiacantha cuspidata having zygospondyline vertebral articulation according to 

 Lyisian. The streptospondyline articulation is a common character of a part of the Ophiaeanthi- 

 dci' and all the Hemîeiiryalidœ among the Lcemophiwlda, as well as of the Ophiohxjrsinœ, 

 Trichastervdai and Gorgonocepftcdkkc among the Fhrynophturida. Ophiolehes tuber osa (fig. i) has 

 short and stout vertebra?, whose wings are rather thick laterally as well as dorsally, also a 

 common character of those forms with streptospondyline vertebral articvilation. The articulation 

 of the genital plate and radial shield is, as shown in the figure, very simple, without any 

 special condyle and socket, a common character of the rhrynop)hmnda, and La'mophiurlda. The 

 genital plate and scale merely articulate with each other, without being soldered together, a 

 character of the Ophiacunlhidœ and some other orders in contrast to the Hemieuryalidcr. 



PI. ni, figs. 7 & 8 illustrate the internal structures of Amphktctis umbonatu, a representative 

 of the Amphilepklidcr. The iieristomial plates are almost simple and very large, a character 

 distinguishing the present family from all the other GnathophiurhJa. The oral i)lates and frames 

 are slender and the latter have no lateral wungs, also a character distinguishing the present 

 family from the other Gnathophhirkla. The dental plate is absent ; this is a peculiar character. 

 The teeth are not very stout and thick, though appearing wide in tlie figure, also a character 

 uf the present family in contrast to the other Gnathophiurida. The genital plates bear a very 

 conspicuotis, ball-like articular condyle on the dorsal side near the outer end ; this is a charac- 

 teristic of the G'nathophiurkîa in contra-Ht to all the other orders. The genital scales are wide, 

 thin and leaf-like and articulate with the genital plates near the outer ends of the latter ; 

 these characters of the genital scales are notable in the Gnathophiurida, though also found in 

 some ChUophiurkla. The dorsal surface of the vertebra is rhomboidal, instead of being strongly 

 notched at the inner end, a common character of the Amphilepklkid' and Amphiwida; in contrast 

 to the Ophwirichklce among the Gnathophiurida . The distal vertebne (fig. 8) are in this species 

 imperfectly divided into halves by a series of pores. Such vertebrœ or those in which the 

 halves are divided by a moniliform pore, are found in several of the genera with the arms 

 perfectly protected by the plates (see also PI. V, fig. 3) ; while vertebr;e with the halves 

 divided by a fusiform pore are found in the Ophiomyxinœ, in which the dorsal side of the 

 arms is largely unprotected. See text-fig. 2 f & g, p. 18. 



PI. Ill, figs. 9-13 and PI. IV, figs. 1-5 illustrate the internal structures of the Amphiuridcv. 

 The peristomial plates of Ophiactis pteropoma (PI. ITT, fig. 9), OphiophoHs aculeata (PI. Ill, fig. 

 10), Hemipholis elongata (PI. IV, fig. 1), Amphioplus ancistrotus (PI. Ill, fig, 11), Amphlacantha 

 diindua (PI. Ill, fig. 12), Ophiophragmus japonicus (PI. IV, fig. 3) and Amphlpholis kochii (PL 

 IV, fig. 2) are simple and very small, a common character of the Amphiurldcc, with the excep- 



