jgg BULLETIN 76, UNITED STATES NATIONAL MUSEUM. 



opposite two superomarginals (four in type). Only one series of paxillse reaches 

 terminal plate, but the two adradial very nearly. In typical specimens papulae 

 are readily seen between paxilhr, generally six about each. 



Dorsal plates or bases of paxilhc are distinctly and often very conspicuously 

 lobed on the proximal radial regions. At tip of ray beyond the papular area the 

 plates become hexagonal or elliptical; along margins of area they lose the lobes, 

 and vary greatly in shape, even becoming triangular; on center of disk the plates 

 are without well-delined lobes and are irregular. On the proximal radial areas 

 there are six lobes to a plate, the plates overlapping by them. These lobes vary 

 freatly in length, being longest and slenderest on typical forms with small paxillse. 

 Papulaj extend along ray nearly to tip (0.7 to 0.8 length measured on side); else- 

 where they are generally distributed except where interradial septum joins abac- 

 tinal surface. 



Margmal plates well developed. Superomarginals, about twenty-five in num- 

 ber from median interradial line to extremity of ray, form a steep, arched bevel to 

 border. Plates wider than long, the width decreasing gradually along ray. They are 

 covered with spaced, low, hexagonal, or roundisli, convex-tipped granules formmg 

 two or three transverse series, with an additional series of smaller, slenderer, often 

 pinched granules on either transverse margin. The larger median granules increase 

 in size towanl outer and lower margin of plate near which are one to three enlarged 

 subtubercuhir granules. 



Inferomarginals correspond to superomarginals in position, and form a similar 

 bevel to ac^tinal surface. They are covered with a spaced papilliform granulation, 

 and a median transverse row of four prominent sharp spinules, which are reduced 

 to two on outer half of ray. Narrow fasciolar channels run transversely between 

 the plates of both series. When denuded of granules the specialized ridges of 

 marginals are seen to be much thicker than intervening channels. Terminal plate 

 ovoid and prominent, the narrower end toward paxillar area. Young specimens 

 have two prominent tubercles at tip, on either side. 



Adanibulacral plates with an angular furrow margin; of this the side toward 

 mouth is shorter tlian tiie aboral; or tlie margin may appear, superficiall}', to be 

 curved. Plates wider than long. Armature consists of (1) a palmate furrow 

 series of four or five cylindrical or slightly compressed, slightly tapering, blunt- 

 tipped spinelets, sometimes swollen and subpapilliform. Rarely there are six or 

 as few as three. (2) On actinal surface is a semicircle of unequal, very small, 

 swollen papilliform spinelets on border of plate, surroundmg a similar but enlarged, 

 often curved, central spinule. The outer plates of the series frequently have the 

 spinelets arranged in two rows, and there are two enlarged spinules; or these 

 spinelets may be arranged in a circle around the enlarged spinule, which increases 

 in prominence toward tip of ray. 



Mouth plates prominent actinally, and the combined pair with a broadly oval 

 contour, the wider end toward actinostome. Armature of margin consists of a 

 prominent median (unpaired) spine, slightly flattened, and on each plate an angular 

 series rising toward peristome very slightly. This series consists of two or three 

 spinelets on margin toward actinostome and about four or five on the furrow margin, 



