OPHIUROIDEA OF THE BAHAMA EXPEDITION. ^ 



A pair of small, round genital pores under the outer end of 

 the oral shields. 



This genus differs decidely from Hemieuryale, to which it 

 is allied, in having distinct and well formed dorsal arm-plates. 

 It is also closely allied to Sigsbeia. In fact, it stands between 

 these two genera in several characters. 



Ohpioplus tuberculosus CZ,ym.) Ver. 



Hemieuryale tuberculosa Lyman, Bull. Mus. Comp. Zool., vol. X, p. 

 276, pi. VIII, figs. 120-127, 1883. 



Ophiomusium (?) Nutting - , Narrative, p. 78. 



Plate i; Figures i, ia, id. 



Disk small, thick, pentagonal or five-lobed, convex, swol- 

 len over the bases of the arms, covered with rather large, 

 mostly rounded, swollen and verruciform plates, among which 

 a central plate and ten radiating rows of radial and interradial 

 plates of larger size and greater elevation can be distinguished ; 

 the smaller plates are more irregular in form and less swollen. 

 The radial shields are rough, rudely elliptical or ovate, rather 

 long, widest in the middle, far apart, separated by a median 

 row of about three high, verruciform pldtes and a row of small- 

 er ones on each side. Upper arm-plates, except the basal, are 

 broader than long, very thick and prominent, transversely el- 

 liptical or oblong, with all the corners rounded; outer end 

 often a little emarginate, and inner end often truncated. They 

 are usually separated by a single row of three, high, verruci- 

 form plates, of which the middle one is round and the laterals 

 ovate; sometimes there is an additional row of two or three 

 plates; at the base of the arms the median one may be lack- 

 ing, and toward the tips, the laterals usually disappear, leav- 

 ing only a small median one. A row of rounded prominent 

 plates extends along each upper edge, alongside of the arm- 

 plates, and alternating with the side-plates . Arm-spines 

 generally two, sometimes three, small, short, stout, the lower 

 one thickest, clavate or obtuse. Tentacle-scale rather large, 

 ovate. 



