268 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



more plates. The first plate has 5 or 6 furrow spines, which in- 

 crease to 10, the laterals being broader than the 2 or 3 mesial spines, 

 which are compressed to an even thickness, but are slightly tapering 

 and round-tipped when seen from the side, as indeed are the laterals. 

 Subambulacral granules 10 to 14, in about three series, the inner 

 slightly longer than the outer. The first few plates have a pedi- 

 cellaria, with two or three coarse tapering, slightly curved, bluntly 

 pointed spiniform jaws. 



Mouth plates small, with 7, rarely 8, marginal prismatic spines, 

 and about 8 pointed tubercular prismatic or 4-sided oral spines in a 

 single row on inner end of plate, becoming 2 rows of granules on 

 outer end. 



Madreporic body pentagonal, surrounded by 5 plates, situated one- 

 quarter r from center. 



Type.— C^t. No. 30543, U.S.N.M. 



Type-locality. — Station 5536, between Negros and Siquijor Islands, 

 Philippine Islands, 279 fathoms, green mud, bottom temperature 

 53.5° F. ; 1 specimen. 



Distribution. — Mindanao Sea, between Negros, Siquijor, and Min- 

 danao. 



/Specimens examined. — The type and a young example from station 

 5541, off Point Tagolo, northern Mindanao, 219 fathoms, fine sand, 

 broken shells, bottom temperature 53.5° F. 



Remarks. — It is not possible with tlie material at my disposal to 

 decide whether this is a distinct species or a variety of N. euryplax. 

 Although N. euryplax, N. mucronatus, and N. dyscritus appear 

 different enough, yet each is represented by but a simple adult speci- 

 men. The course taken seems best even if it is later established that 

 they are 3 phases of one species. The characters used to discriminate 

 them are the same that have been employed in separating other forms 

 represented by several examples. The range of variation in Nym- 

 phaster is not yet well understood, 



N. dyscritus differs from N. teiYialis Perrier in having less tumid 

 marginal plates, smaller abactinal radial plates, a sharper, more 

 abrupt angle to margin of ray, longer superomarginals in proportion 

 to their width (on ray), and in having the marginal apophysis on all 

 the adambulacral plates (although not conspicuous on the first half 

 dozen). N. dyscritus greatly resembles N. t emails of Koehler (but 

 not of Perrier) from the Indian region, and I shall not be surprised 

 if they ultimately turn out to be races of the same species. Koehler's 

 species has more regularly hexagonal abactinal plates, 8 adambulacral 

 furrow spines (maximum?), more numerous adambulacral pedi- 

 cellariae (easily a variable character), 8 or 9 mouth spines, and the 

 apophysis commences between the third or fourth and fifteenth 

 adambulacral plate, varying on different specimens. These differences 



