MONOGRAPH OF JAPANESE OPHIUEOIDEA. 385 



rnyxidtv in contrast to the Trichasteridœ and Gorgonocejjfutlvlo: The vertebra is moderately 

 short and stout (PI. II, fig. 1), being shorter and stouter than that of the Ophîomyxinœ bitt 

 not so very short and stoixt as in the Trichasteridœ and Gorgonocephalida; a characteristic 

 of the Ophidbyrsino'. The wing of the vertebra is very thick laterally as well as dorsally, a 

 common character of the Ophidbyrsinœ, Trichusieridœ and Gorgonocephalida'. As the specimen, 

 from which the illastration has been made, is very small and young, the characteristic shape of 

 the vertebra is not yet fully developed ; the vertebrre near the disk of full-grown specimens of 

 the Ophidbyrsinœ are much more stout and more distinctly discoidal. PI. I, figs. 12 & 13 show 

 the two forms of arm spines of OphiosmUax mirabilis, both being converted into c impound 

 hooks. It is noteworthy, that the arm spines of the majority — presumably all — of the I'hryno- 

 phiurida are always book-shaped in their embryonal stages, as observed in the distal arm 

 joints. 



PI. I, figs. 14-16 illustrate the internal structures of Asteronyx loveni. a representative of the 

 Aster onychînœ. The peristomial plates are simple, stout and firmly soldered to the oral frames, 

 which are also very stout, common characters of the Ophiohyrsina\ Trichasteri/Jœ and Gorgono- 

 cephalida; in contrast to the Ophio7vyxina.\ The veiy basal vertebrre are not notably shorter 

 than the outer; all the vertebra; are short, stout and discoidal; and the vertebral articulation is 

 typically streptospocdyline or saddle-shaped ; all th( se characters are common to the Ophio- 

 tyrsina?. Tricha stirida; and Gorgonocephalida'. The upper muscular fossae are fairly large and 

 the lower rather small ; this character is rather intei mediate between those of the Opîdoiiiyxidc' 

 and of the other Trichasterida', for the upper and lower muscular fossa; are subequal in size in 

 the former and very unequal in the latter. The relatively small inequality between the ujjper 

 and lower fossa' here illustrated may partially be due to the youngness of the specimen. The 

 genital jjlates are high in position relatively to the basal vertebra; ; this character also approach- 

 es to that of the Ophiomyxidœ. The genital scales articulate with the genital plates near the 

 inner ends of the latter, a characteristic of the Asieronychkuv in contrast to the Trlchasterina?, 

 Asteroschemalina: and Gorgonocephalida:. The articulation of the genital plate and radial shield 

 is very simple, without any particular condyle and socket, a common character of the Fhryno- 

 phiurida and La'mopjhiurida. 



PI. n, figs. 7 it 8 illustrate the skeletal structure of Trichaster elegans, a representative of 

 the Trichasterina'. The oral plates are very stout, a common character of the Ophiobyrsina', 

 Trichasteridœ and Gorgonocephalida^ The adorai shields are also large and stout, a character of 

 the Ophiomyxidœ and Trichasterida; in contrast to the Gorgonocepjhulida' ; a jjeculiar feature is 

 that they are divided into inner and outer halves. The lateral arm plates of the two sides are 

 separated from each other by the ventral arm plates, a character of the Asteronychiva' and 

 Trichasterina; in contrast to the Ast roschematina;. The ventral arm plates are divided into two 

 or three secondary plates, a peculiar feature. The interbrachial area is very small and the 

 genital plates and scales are very closely set side by side ; this is a generic character. That the 

 genital scales do not lie far inward from the oiüer ends of the genital plates is a common 

 character of the Trichasterina', Asteroschemathxa: and Gorgonocephalida: in contrast to the 



