NO. 1944. .V/?1F GENERA AND SPECIES OF STARFISHUS— FISHER. 619 



Type-locality. — Station 5114, Balayan Bay, southern Luzon, 340 

 fathoms, fine sand. 



The inferomarginal plates extend slightly beyond the superomar- 

 ginals and are very narrow, with a tumid outer end, as in cediplax. 

 Except for the first 2 or 3 plates, wliich are wider than long, all the 

 plates are either as wide as long (to about the middle of ray) or nar- 

 rower than long (outer half of ray). For this genus the inferomar- 

 ginals are very narrow and form a narrow, slightly beveled border to 

 the actinal area. Lateral spines proximally 3 (with sometimes a slen- 

 derer fourth spine at the upper end of the series), distally 2, slender, 

 slightly cuived, appressed, the lowest the longest, and equaling 2^ 

 to 2f plates in length on the proximal haK of the ray. On the 

 distal margin of the narrow actinal facet of the plate 2 or 3 much 

 smaller, very slender spinules continue the lateral series. These 

 become so small on the outer third of ray that they merge into the 

 general spinulation, and owing to the extreme narrowness of the 

 plates the lateral comb occupies the whole ^N'idth. The spinelets 

 covering the outer or lateral face of the plate are delicate, terete, and 

 upright hke those of the superomarginals, but actinally they become 

 coarser, sharper, and well spaced. There may be on the proximal 

 plates an additional enlarged spinule near che adoral margin. Several 

 ■plates in the interradial area, adjacent to the adambulacrals, bear 

 prominent fasciculate pedicellarise with 4 to 6 swollen spinifoim jaws, 

 the calcareous portion being very slender. The furrow spines are 

 5, or occasionally 6, long, slender, compressed, pointed, membrane- 

 invested, and webbed at base, forming a regular comb with a curved 

 outer margin. The mesial spines are about as long, on the proximal 

 third of the ray, as the neighboring inferomarginal plate. Subam- 

 buKcral spines very slender, terete, but apparently thick and swollen 

 owing to the translucent tissue investing them. There are about 6 of 

 these forming 2 series on the second and third plates, then on the 

 succee(fing plates a single zigzag series, and finally on the outer half 

 or two-thirds of the ray 2 more or less iiTegular series of 8 bo 12 

 spinules. 



This species is an aberrant Persephonaster in that its marginal and 

 mouth plates are distinctly smaller than the mean for the genus, and 

 the general habit is slender. The actinal interradial areas are un- 

 usually small, and the furrow spines of the adambulacral plates reach 

 the lowest number known in the genus. P. Tiabrogenys agi'ees with 

 P. gracilis (Sladen) (formerly Psilaster gracilis) in having small 

 mouth plates, but differs in possessing armed superomarginals, 

 smaller disk, higher paxilla?; in having the lateral and ventral facets 

 of the inferomarginals better differentiated, and the long inferomar- 

 ginal spines lateral in position ; in having fewer furrow spines. 



