232 BULLETIN 76, UNITED STATES NATIONAL MUSEUM. 



marginal series of granules as in (he two preceding species, but are elliptical as a 

 rule (most of the spine-bearing plates are subcircular) and immersed in a soft mem- 

 brane, from which the spmes, pedicellarije, and elevated portions of the plate 

 emerge. The small unequal, conical, subspherical, and acorn-shaped granules are 

 immersed in this membrane, and are scattered irregularly and rather sparsely over 

 the exposed portions of the plates and intermediate ossicles. On some of the 

 secondary plates a granule assumes the proportions of a small acorn-shaped tubercle. 



Wlien the abactinal skeleton is. viewed from the inner or coelomic surface, it 

 presents a very characteristic appearance. The primary plates are connected by 

 irregularly radiating ridges composed of ossicles placed end to end. The bottom 

 of the intermediate ossicles or plates is much compressed, so that the ridges formed 

 by them are narrow. The height of the ossicles causes the enclosed space to appear 

 as a pit, the skeleton assuming a honeycombed or fenestrated appearance. The 

 meshes of this skeleton are further subdivided by a few smaller low trabeculse 

 near the surface. These separate the papulse, are incomplete, and do not interfere 

 with the honeycombed structure mentioned above. (See PI. GO, fig. 6). Tlie papulae 

 are very conspicuous in the undried state (2 mm. long) and are distributed all over 

 the abactinal surface. 



Marginal plates not particularly conspicuous. Superomargmals, fifteen in 

 number from median interradial line, slightly convex, and confined to side of body; 

 first plate larger than the rest, wliich are rather longer than high except at end of 

 ray, where the reverse is true; upper eilge of the series largelj' obscured by abactinal 

 membrane. Each plate on proximal half of ray (first to fifth or sixth) bears a 

 sessile bivalved pedicellaria and in addition one to four spines like those of the 

 abactinal surface. Edge of plate (excepting usually the upper) is armed with one 

 or two interrupted series of stout conical granules of various sizes. Outer plates 

 of series have a single central spine and marginal granules in one or two irregular 

 series. Inferomarginals corresponding in number to superomarginals aad oppo- 

 site them in proximal third of ray, but alternate on outer part; they encroach some- 

 what upon the actinal area, the lower margin being obscured on the disk by the 

 membrane covering the general surface of the plates. Nearly all the plates bear 

 a bivalved pedicellaria and, in addition, on the first two plates of the series a circle 

 of four or five spines (like the superomarginal spines) surrounding it, on the rest 

 two or three, wliich are situated on the aboral side of the plate. There are also on 

 the border of each plate numerous stout conical tubercular granules mixed Avith 

 small ones, the former occasionally having one or two enlarged into conical spinules, 

 intermediate in size between the spines and larger granules. The pedicellaria^ of 

 the marginal j>lates are exactly like those of the abactinal surface. 



Adambulacral armature, consisting of two heavy cylindrical or slightly com- 

 pressed l)lunt furrow spines, the adoral a trifle the smaller on outer half of ray; and 

 on actinal surface a transverse series of two similar spines rather more tapered, the 

 outer the sliorter, occupying all the exposed surface, the outer spine reduced in size 

 on the fii'st few plates. Margin of plate surrounded by conical granules, one or two 

 on the outer edge larger than the rest. 



Mouth plates small, narrow; furrow margin very extensive; furrow spines four, 

 similar to those of adambulacral plates, the innermost slightly longer and most 



