386 ART. 2. — H. MATSÜMOTO : 



Aster onychince. Text -fig. 8 h-ü (p. 38) muy also be referred to here. The upper imiscular fossîe 

 of the vertebra are much larger than the lower, a common character of the Trichasteridcp. and 

 Oorgonocephnlidœ ; each dorsal arm plate being represented by a pair of triple rows of nodule- 

 like secondary plates is a generic character ; that each dorsal arm plate is represented by a pair 

 of secondary plates or of groups of secondary plates in the basal arm joints containing the 

 generative glands, is a common character of Astroceras, Trichasler and Asteroschema., 



PI. II, figs. 2-6 iUustrate the internal structure of Asteroschema japonicum, a representative 

 of the Asteroschemalina\ The very stout peristomial plates which are firmly soldered to the 

 also very stout oral frames, the short and stout and markedly discoidal vertebr;«, the strepto- 

 spondyline vertebral articulation, the markedly unequal tipper and lower muscular fossne of the 

 vertebrae, the very simple articulation of the genital plate and radial shield, and the position of 

 the genital scales in relation to the genital plates, are characters which have been already 

 explained. The lateral arm plates are transversely bar-like, and those of the two sides are in 

 contact with each other in the ventral median line, thus separating the very small ventral arm 

 plates from one another, a characteristic of the Aster oschematinœ. Each dorsal arm plate is 

 represented by a pair of bar-like rows of secondary plates ; this is a generic character, though 

 the fact that each dorsal iilate is represented by a pair or groiip of secondary plates is a 

 common character of Astroceras, Trichaster and Asteroschema, as already explained. 



PI. II, figs. 9 & 10 illustrate the internal structure of Astrotomn sobrina, a representative of 

 the Astrotomina; {Gorgonocephalida;). The common characters of the Trichdsterldœ and Gorgono- 

 cepalidce are sufficiently exf)lained in the text. The basal vortebrre are much narrower and smaller 

 than those beyond, a characteristic of the Astrotominœ in contrast to the Gorgonocephalinœ. They 

 are covered over by the muscles between them and the genital plate, also a characteristic of the 

 Astrotominœ. The adorai shields are very small and insignificant, a characteristic of the 

 Gorgonocephalidœ in contrast to the Trichaster idee. The area just inside the interbrachial 

 ventral surface is occupied by a mosaic of supplementary plates, a characteristic of the Astro- 

 tominœ in contrast to those genera of the Gorgonocephalinœ with arms simple or divided a few 

 times, and a common character of the Astrotominœ and those genera of the Gorgonocephalinœ 

 with arms divided many times. The common character just mentioned may 1)9 due to convergence. 

 PI. II, fig. 11 shows a compound hook of an arm annulus of As',rothamnus echinaceus. Such a 

 compound hook with more than two supplementary booklets besides the terminal one is 

 imcommon among the Gorgonocephalidœ.. The compound hooks of the arm annuli of Astrotoma 

 sobrinn belong partially to this type with two or three supplementary booklets and j)artially 

 to the common type with only a single supplementary booklet besides the terminal one. 



PI. Ill, figs. 1-6 illustrate the internal structures of the Ophiacanthidœ. The peristomial 

 plates of Ophiacantha hidentata (fig. 1), Ophiolehes tu'jerosa (fig. 4), Ophiolimna antarctica (fig. 5) 

 and 0. papUlata (fig. 6) are almost or perfectly entire and very large, characters common to most 

 of the genera of the Lœ.mophiurida and certain groups of the other orders. That the peristomial 

 I)lates of the two species of Ophiolimm just mentioned are almost entire and very wide and 

 short, is a proof of their Ophiacauthine, and not Ophiodermatine, affinity ; the peristomial plates 



