OPHIURANS OF UNITED STATES NATIONAL MUSEUM. 97 



The under part of the disk in the interradial spaces appears covered with 

 imbricated and distinct scales, especially in its proximal half. It shows, near the 

 margin, spines which are rather close to one another, and identical with those of 

 the upper face, but the granules are very scarce; the spines arc farther apart and 

 shorter proximally, advancing, however, up to the neighborhood of the mouth 

 shields. 



The latter are very large. Their cliief part is triangular, wider than long, 

 with a fairly sharp proximal angle, the apex of which, though, is generally somewhat 

 rounded and limited by two straight or slightly incurved sides; the side angles are 

 broadly rounded, and the distal side is occupied on most of its length by a wide and 

 much protruding lobe, having a rectangular shape, rounded lateral angles, and a 

 free margin, which is itself rounded and may carry one or two spines identical with 

 the neighboring ones. The adoral plates are extremely thin and most elongated; 

 they become a little thicker internally and grow up so as to lean against each other 

 for a certain length, following the interradial median line; they also grow a little 

 wider outwardly, embracing the external angle of the mouth shield, but they supply 

 only an extremely narrow blade, which scarcely separates this shield from the first 

 brachial side plate; their two margins are slightly sinuous, and the free margin is 

 rather deeply notched on the level of the large tentacular oral pore. The oral 

 plates are large, high, and quadrangular, with parallel margins. They show on 

 their free edge a set of oral papillae, of medium size, conical and pointed ; then, on 

 the level of the tentacular oral pore, there appear two very long cylindrical and 

 pointed spines, which are of equal size, one of which is still inserted on the oral 

 plate, while the other issues from the adoral plate. On the under face itself of the 

 oral plates I observed in but one case a papilla located near the distal edge. At 

 the proximal end of each oral plate there is found a large conical papiUa, larger than 

 the neighboring oral papillae, but it does not seem to me that there should be other 

 papillae in the same region, although I find in one place two very unimportant little 

 sweUings; moreover, these parts are far from being entire. 



The fu-st upper brachial plates have their outlines almost completely hidden 

 by the conical gi-anules which cover them all over; they seem to me likely to be 

 more or less divided up. The plates which come next to the aforesaid, and only 

 two or thi-ee of which are preserved, are rather narrow, a little longer than wide, 

 triangular, with a rounded proximal angle limited by two slightly convex sides, 

 joining by broadly rounded angles the very convex distal side. All the preserved 

 plates are contiguous. 



The first under brachial plate is elongated and narrow, triangular, with a 

 concave distal side and a very acute proxunal angle; it is ah-eady separated from 

 the second one. All the other succeeding plates may be considered as pentagonal, 

 with an extremely obtuse proximal angle, limited by two concave sides, two diver- 

 gent lateral sides, which are deeply excavated by the large corresponding tentacular 

 pores and united to the distal side by elongated and acute angles ; this distal side is 

 very \vide and shows in its middle a strong notch. The proximal part of the plates 

 is always narrower than the distal part, and these plates are narrowed in their 

 middle. They are all longer than wide and widely separated by the lateral plates. 



