344 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



the plates of the papular areas the granules are visible, but over all 

 the interradial areas they can not be seen, although the skin is pitted 

 somewhat over the interspaces between the granules. When the 

 membrane is partially dried the granules become visible. In this 

 soft membrane the pedicellariae have depressions for the opened 

 jaws. 



When the abactinal integument is cleared, and viewed from the 

 coelomic side the plates are seen to be spaced. In form they are not 

 at all uniform, varying from irregularly roundish to lozenge or 

 ellipical, and the inner end is convex. The outer end flares, being 

 larger than the inner, and of the various forms mentioned above. 



Superomarginals, about 80 to a ray, are dorsally conspicuously 

 wider than long, and form a beveled margin, sometimes a trifle 

 arched, to the abactinal surface. They encroach upon the actinal 

 surface about one-half as far as upon the abactinal, and thus form the 

 margin of ray. The convexity of the lateral angle of each plate 

 causes the margin of the ray to appear scalloped, except near the ex- 

 tremity. The plates are closely covered with small granules, similar 

 to those of the abactinal plates, overlaid by soft membrane, so that 

 they are very indistinct, or even invisible. On the proximal half of 

 the ray the dorsal surface of the superomarginals bears 2, or rarely 

 3, small pedicellariae, similar to those of the abactinal plates, while 

 the ventral surface bears 1; the dorsal surface of the plates of the 

 distal half of ray bears one such pedicellaria. 



Inferomarginals very slightly convex proximally, corresponding to 

 superomarginals, but along the middle region of ray not exactly 

 corresponding. First 10 plates slightly wider than long, gradually 

 becoming slightly longer than wide over most of the ray. On the 

 outer fourth of ray the inferomarginals are only a trifle larger than 

 the adambulacrals. The plates are entirely confined to the actinal 

 surface and beyond the interbrachium are only a little wider than 

 the ventral facet of the superomarginals — that part which extends 

 laterally beyond the ventral series. Over a little more than the 

 proximal half of the ray the plates bear, near the outer margin, a 

 small 2- jawed spatulate pedicellaria, and rarely a second elsewhere 

 on the plate. When the animal is viewed from the oral side 3 series 

 of plates occupy the entire width of the surface between the furrow 

 and ambitus, on the outer half of the ray — the adambulacral, infero- 

 marginal, and superomarginal series, the first and last of about the 

 same width, the inferomarginals slightly the widest. The granules 

 increase slightly in size from the outer toward the inner margin and 

 are immersed in membrane, with often the tips protruding. 



Actinal interradial areas extensive with numerous irregular 

 slightly convex plates, without regularity of arrangement, and ex- 

 tending in a single series nearly half the length of ray, a second 



