272 BULLETIN 100, rXITED STATES NATIONAL MUSEUM. 



Type-locality. — Station 5116, mouth of Balaj'^an Bay, Luzon (o^ 

 Verde Island Passage, north coast of Mindoro), 200 fathoms, bottom 

 temperature, 50.2° F. 



Remarks. — Although this species resembles iV. euryplax in many 

 ways, it presents numerous points of difference which have already 

 been mentioned in the diagnosis and description. The most con- 

 spicuous of these are the smaller and much less compact abactinal 

 plates with their mucronate granules, the narrower inferomarginals, 

 coai^ser and unequal actinal intermediate granules, the very small 

 mouth plates, and the enlarged subambulacral spines. 



N . mucronatus differs from N. helU, to which the form of the radial 

 plates would ally it, in having mucronate granules, larger madreporic 

 body surrounded by 6 plates, inferomarginals extending laterally 

 beyond superomarginals, larger, unequal acorn-shaped, often incipi- 

 ently mucronate, actinal intermediate granules, smaller mouth plates, 

 and numerous stout subambulacral spines. 



NYMPHASTER LEPTODOMUS Fisher. 



Plate 66, fig. 1; plate 67, fig. 1; plate 68, fig. 3; plate 69, fig. 3; plate 92, 



figs. 2, 2o-&. 



Nymphaster leptodomus Fisher, 1913a, p. 637. 



Diagnosis. — In the form of the abactinal plates resembling .V. 

 mucronatus., but differing in having longer, slenderer rays, narrower 

 superomarginals, inferomarginals extending little or not at all be- 

 yond superomarginals, subspherical, depressed, sometimes truncate 

 abactinal granules, abactinal, spatulate pedicellariae, larger mouth 

 plates, 8 to 10 oral spines, adambulacral pedicellariae, and no con- 

 spicuously enlarged subambulacral spines. Eay very slender, vary- 

 ing from plane to convex above, the width at inner end of the first 

 pair of superomarginals which meet medially equal to length of first 

 3 superomarginals measured along side; adambulacral furrow spines 

 proximally 6, distally 10 or 11. E=70 mm., r=17.5 mm., E=4 r; 

 breadth of ray at midinterbrachium, 20 mm. 



Description. — Abactinal area arcuate-pentagonal to stellato-pentag- 

 onal. Eadial plates broader than long, at least for the 5 median 

 rows, the midradial the broadest, elliptical to broadly hexagonal or 

 lozenge-shaped, with a variable number (usually small, 2 to 6) of 

 spaced central granules in 1 or (proximally) 2 transverse rows, and 

 15 to 18 slightly smaller peripheral granules. These granules are 

 variable in form, convex, or truncate, roundish. Many of the radial 

 plates have a narrow spatulate 2- jawed pedicellaria, the jaws, when 

 open, reaching nearly across the plate. Papular areas broad, peta- 

 loid, comprising 9 to 11 longitudinal series of plates. Interradial 

 areas small, with small four-sided or five-sided not very regular 



