STARFISHES OF THE PHILIPPINE SEAS. 65 



PRIONASTER GRACILIS Fisher. 



Plate 3, fig. 2 ; plate 6, fig. 1 ; plate 9, fig. 1, lor-b. 

 Prionaster gracilis Fisher, 1913o, p. 603. 



Diagnosis. — Differs from Prionaster analogue in having conspicu- 

 ously longer rays, with a distally wider paxillur area which reaches 

 terminal plate; paxillae with slenderer, sharper spinelets; madre- 

 poric body larger, with different striation; superomarginals nar- 

 rower abactinally; cribriform organs open and exposed proximally; 

 longer marginal spines; more numerous adambulacral spinelets; first 

 adambulacral not compressed; double series of interradial actinal 

 plates wider at inner or central end; enlarged subambulacral on mid- 

 dle portion of ray only. E=165 mm., r=24 mm., E=6.9 r; breath of 

 ray at base, 24 mm., at tenth inferomarginal, 14 mm. 



Description. — Eays very long and slender throughout the whole 

 length. Paxillae small and crowded, about the same size as in 

 analogus, but the spinelets slenderer, tapering, and bluntly pointed, 

 not capitate or clavate as in analogus. The paxillae decrease in size 

 from the proximal radial region toward the end of ray and center of 

 disk. About 9 paxillae correspond to the first 2 superomargi- 

 nals. There are about 14 spinelets to a large paxilla. At middle of 

 ray the paxillar area is 2.5 times the width of dorsal surface of su- 

 peromarginals. The paxillae reach the terminal plate. 



Abactinal plates lozenge-elliptical and more or less irregular on 

 the ray, becoming more circular, with indications of 4 to 6 sides 

 on the disk. On the rays the plates are slightly spaced, but just 

 touch one another on the disk. The papulae extend nearly to tip of 

 ray and are absent from a narrow radial strip, and from center of 

 disk. 



Superomarginals, 74, the distal plates about as wide as high (much 

 wider than high in analogus)., and the last 4 plates nearly touch 

 the opposite ones medially. The paxillar area is wider distally than 

 in analogus., and fewer marginals approach the median line despite 

 the much longer ray. Cribriform organs much more open than in 

 analogus and even more open than in Goniopecten asiaticus, espe- 

 cially between inferomarginals. In the interbrachium the width of 

 the exposed portion of organ (exclusive of marginal web) is about 

 1.5 mm., or a little over one-third height of superomarginal, or one- 

 half lateral face of the inferomarginal. The organs become nar- 

 rower very gradually toward the end of ray. The marginal spines 

 are as in analogus but are longer. Terminal plate with apparently 

 but 4 terminal spines (only 1 ray perfect). 



The interradial double row of actinal intermediate plates (7 in 

 each series) is much broader at the inner end, therefore more wedge- 

 shaped, than in analogus, owing to the fact that the first adambu- 

 lacral plate is not compressed. The interradial area proper extends 



