264 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



e\ Marginal plates iudivitlually tumid; uo adambulacral pedicellariue ; 

 mouth spines 9 or 10 ; furrow spines 9 to 11 at middle of 



ray arthrocMemis, p. 277. 



e*. Marginal plates not individually tumid ; adambulacral pedicellariae ; 



furrow spines at middle of ray more than 11. 



f. Dorsolateral angle of ray about 90°, square cut ; dorsal surface 



plane; marginal granulation closer; sixth and sometimes fifth 



superomarginal longer than width of its dorsal surface; 10 



inferomarginals corresponding to about 16 adambulacrals ; 



mouth spines 9 to 11 mesercs, p. 280. 



f. Dorsolateral angle of ray more rounded, the dorsal surface being 

 convex ; marginal granules more spaced ; ninth or tenth supero- 

 marginal longer than width of its dorsal surface ; 10 infero- 

 marginals corresponding to 13 or 14 adambulacrals ; mouth 

 spines 12 to 15 habrotatus, p. 282. 



NYMPHASTER EURYPLAX Fisher. 



Plate 63, fig. 3; plate 72, fig. 2; plate 92, figs. 6, 6«. 

 Nymphastcr curyplax Fisher, 1913a, p. 634, 



Diagnosis. — General form, similar to that of N. diomedeae Ludwig 

 and N. ternalis (Perrier), but superomarginals with plane abactinal 

 surface, not tumid ; rays broad at base and actinal surface conspicu- 

 ously wider than abactinal, the edges between the 4 faces of the ray 

 Ijeing abruptly angular, disk arcuately pentagonal, gradually merg- 

 ing into rays at corners ; extreme width of ray, measured at proximal 

 suture of the first pair of superomarginals which meet medially, 

 equaling length of first 4 or 5 superomarginals, measured on ambitus ; 

 inferomarginals broad; rays not sunken along median radial line; 

 inferomarginals broader than superomarginals on disk, but narrower 

 on ray; radial and adradial abactinal plates broader than long, hex- 

 agonal, elliptical, and lozenge-shape ; adambulacral plates with very 

 strong furrow angle and 9 or 10 furrow spines, the apices of the 

 angles of opposite plates meeting in middle of furrow and segregat- 

 ing consecutive pairs of tube feet beyond proximal fourth of furrow; 

 mouth plates with 6 to 8 marginal spines; no pedicellariae except 

 rarely on the first few adambulacral plates. K= slightly over 95 

 mm. (ray broken), r=:27 mm. R=a little over 4 r. 



Descrnqytion. — Abactinal area arcuately pentagonal in shape; peta- 

 loid papular areas broad, the extreme width comprising about 10 to 

 12 longitudinal series of plates; plates rather compactly placed, 

 those of radial and 2 adradial series much wider than long, hexago- 

 nal, lozenge-shaped or rather pointed ellipitical, the others of the 

 papular areas roundish or subhexagonal, often slightlj^ wider than 

 long. A large radial plate has 5 to 12 central, low, subspherical 

 uncrowded grqinules and upward of 20 squarish depressed periph- 

 eral granules a trifle smaller. On the lateral parts of papular areas 

 the central granules become more convex with a short incipient 

 mucronate tip; interradial granules flat-topped. No pedicellariae. 



