MONOGRAPH OF JAPANESE OPHIUROIDEA. 35 



Key to Japanese genera of Trichastevinœ. 



A — Arms simple ; generative glands extending into the &rm. bases as 

 two pairs of ribbon-like bodies ; in basal arm joints of adult speci- 

 mens, each dorsal arm plate is represented by a pair of transversely 

 bar-like plates, which bear a stumpy tubercle at the upper end . . 



Asiroceras. 



AA — Arms dichotomously divided. 



a — Arms divided only near the tip ; generative glands extending into 

 the arm bases as four pairs of ribbon-like bodies ; in basal arm 

 joints of adult specimens, each dorsal arm plate is represented by a 



pair of about triple rows of nodule-like plates TricJiaster. 



aa — Ai*ms divided nearly from the base ; generative glands confined to 

 the disk ; dorsal arm j)l^tes always very insignificant Euryale. 



Astroceras ijergainena Lyman. 



Astroceras percjamena : Lyman, Bull. Mus. Comp. Zool., VI, 1879, p. 

 62, PL XVin, figs. 478-480; Lyman, Kep. Challenger, V, 1882, p. 284, 

 PL XXXIV, figs. 1-5; Clark, Zool. Anz., XXV, 1902, p. 671; Kœhler, 

 Exp. Siboga, XLV, Pt. 1, 1904, p. 159; Clark, BulL U. S. Nat. Mus., 

 LXXV, 1911, p. 284; Döderlein, Abh. Math.-Phys. KL K. Bayer. Akad. 

 Wiss., Suppl.-Bd. I, 1911, p. 61, PL VI, figs. 4-4 &, PL Vm, fig. 13. 



AsiroscJiema sp. ; Döderlein, ibid., p. 57, PL VII, fig. 3. 



Numerous specimens ; Sagami Sea ; 100 fathoms. Numerous 

 specimens ; off Ukislaima, Uraga Channel ; 300 fathoms. 



Eastern Sea ; 95-106 fathoms (Clakk). Yenshii Sea ; 565 

 fathoms (Lyman). Off Omai Zaki ; 34-37 fathoms (Clark). Suruga 

 Gulf ; 52-180 fathoms (Claek, Döderlein). 



Timor ; 216 m. (Kœhler). 



The largest one of my specimens is 7 mm. across the disk. 

 The first ten basal free joints of the arms are wide and provided 

 with transverse plates, which form ridges on either side and are 



