no. 1827. NEW GENERA OF STARFISHES— FISHER. 423 



being immersed in a membrane which nearly or quite obscures the 

 outlines. Inferomarginals correspond with superomarginals prox- 

 imally; distally they alternate. Proximally they bear on the actinal 

 surface one to several very small spatulate excavate pedicellarige 

 with narrow smooth jaws. 



Abactinal plates hexagonal, in regular radial and parallel series, 

 smooth except for scattered minute elevations (not granules) and 

 bordered by a single complete series of flat immersed granules, squar- 

 ish or oblong in shape. Papulae in a petaloid radial area, 6 about 

 each plate. Here the plates are sensibly elevated, although not at 

 all markedly tabulate. If somewhat higher they would be called 

 tabulate. No secondary, smaller, intermediate plates. Small scat- 

 tered abactinal pedicellarise. 



Actinal intermediate plates not very regular either hi shape or 

 arrangement but four-or five-sided, very smooth and with numerous 

 small pedicellarise, especially near furrow. They extend slightly 

 beyond middle of R. 



Adambulacral plates with slightly curved furrow margin, bearing 

 proximally 6 to 8, farther along ray 9 or 10, short, blunt, granuliform, 

 subequal spinelets, the mesial more or less compressed with edge to 

 furrow, the lateralmost somewhat thicker and prismatic or flattened 

 with side to furrow. Border of plate with a row of unequal subcorneal 

 immersed granules, and several on the surface, usually forming a 

 longitudinal series spaced from furrow comb. One or two small 

 pedicellarise usually present, often taking the place of several granules 

 or surrounded by a smooth area. Mouth plate small, with 8 furrow 

 spinelets and a granular actinal surface. 



Madreporic body hexagonal, one-fourth minor radius from center 

 of disk. Furrow narrow; tube feet with strong disks. 



Type-locality. — Station 5272, western Luzon, 25.5 miles southwest 

 Corregidor Light, lat. 14° N.; long. 12° 22' 30" E.; 118 fathoms; mud, 

 shells, and coral sand. 



Type.— Cat. No. 28658, U.S.N.M. 



Remarks. — Abactinally this species resembles somewhat a Plin- 

 thaster with long slender rays, but has perfectly smooth marginals. 

 Barring this it would bear to Plinihaster much the same relation that 

 Nymphaster does to Ceramaster. The actinal intermediate plates, in 

 contradistinction to those of Plinihaster, are smooth, not granulate, 

 and the smaller secondary abactinal plates which are variously devel- 

 oped in Plinthaster are absent. The genus seems to be most nearly 

 related to Iconaster. It differs from Astroceramus, another relative, in 

 lacking the coarse marginal and actinal granules and tubercles, and 

 the specialized, robust subambulacral spines. In some species of 

 Astroceramus the adambulacral armature approaches that of the 

 Hippasteriinse. 



