MONOGRAPH OF JAPANESE OPHIUROIDEA. 37 



this species. I have -five-armed specimens, in which two of the 

 arms are smaller and are undoubtedly regenerated ones ; so that, 

 the five-armed condition may be attained by the final regeneration 

 of only two arms in place of three, in the equally divided halves 

 of six-armed individuals. 



Key to species of Trichaster. 



A — Interbracliial ventral surfaces extremely narrow, so that the two 

 genital slits are so close together as to form a single ajperture ; 

 arms almost triangular in section ; about sixty-two arm joints within 

 the first bifurcation ; each proximal arm joint bearing a pan' of 

 stumpy tubercles on the dorsal side ; arm width at the first bifurca- 

 tion being about one-third of that at the base palmiferus. 



AA — Interbrachial ventral surfaces not extremely narrow, so that the two 

 genital slits are rather well separated from each other ; arms quad- 

 rangular in section ; thirty-nine to fifty-three, usually forty-five, 

 arm joints within the first bifurcation ; arms entirely free of stumj)y 

 tubercles; arm width at the first bifurcation being less than one- 

 fourth of 'that at the bass elcgans. 



Trichaster pahnifertis (Lamarck). 



Euryale palmiferum : Lamarck, Hist. Nat. Anim. sans Vert., II, 1816, 

 p. 539. 



Trichaster palmiferus : Agassiz, Mem. Soc. Sei. Nat. Neuchatel, I, 1835, 

 p. 139^^ ; MÜLLER & Troschel, Sys. Ast., 1842, p. 120 ; Lyman, Rep. 

 ChaUenger, V, 1882, p. 267; Clark, Bull. Ü. S. Nat. Mus., LXXV, 1911, 

 p. 287 ; DÖDERLEIN, Abh. Math.-Phys. Kl. K. Bayer. Akad. Wiss., Suppl.- 

 Bd. I, 1911, p. 62 ; Bomford, Bee. Ind. Mus., IX, Pt. 4, 1913, p. 220, PI. 



xni, fig. 2. 



Trichaster frageUifer : V. Martens, Wieg. Arch. Nat., XXXH, 1877, 

 p. 87.^^ 



1) These papers were not seen by me. 



