EASTERN TROPICAL PACIFIC ASTEROIDEA. 93 



oral surface being quite unusual. The very high and steep jaws are no less 

 remarkable, so that entuTly apart from the pecuUar shape the species will be 

 easily recognized when next it is taken. 



Hymenaster trias,' sp. nov. 

 Plate 3, fiR. 1, 2. 



Rays 5. R = 40 mm.; r = 28 ram.; R = 1.43 r. Body highly arched, 

 the vertical diameter at center being about 20 mm. but this may be due in part 

 to marginal contraction. Form distinctly stellate, the interbrachial arcs being 

 rather deep and angular. Rays quite acuminate, the free narrow tip, about 

 8 mm. long, being turned up against the aboral surface of the ray. Paxillae 

 covering the whole dorsal surface, the interbracliial areas, as seen from above, 

 practically wanting. PaxiUar spinelets five to eight usually six, longer than 

 stalk, very slender and projecting through the thin supra dorsal membrane for 

 nearly or quite half their length. Spiracula fairly numerous, quite large, irregu- 

 larly scattered. Osculum large, about 10 mm. across; each valve with twelve 

 to fourteen spines of which the outermost are shortest but are about three fourths 

 or at least two tliirds as long as the middle ones. Actinolateral spines few and 

 widely spaced; there are about sixteen of which the fifth is longest. The mem- 

 brane in which they lie is thin and transparent. Adambulacral armature con- 

 sists of two well-spaced, subequal, slender, brittle spines, 4-5 nrni. long; the tip 

 is blunt and the spines are not at all sacculate. Aperture papilla distinctly 

 stalked, the blade about as wide as high, except that the upper margin has more 

 or less of a membranous extension, which is, however, never very great. Oral 

 plates united to form a very wide jaw, the width being considerably more than 

 twice the length; the median keel is quite conspicuous but slopes gradually to 

 the inner tip which is wide and rounded; each plate carries three oral spines, of 

 which the innermost is as long as the jaw, or longer, and stands a trifle back 

 from the margin and the outermost is about two thirds as long and stands on 

 the margin near the outer proximal corner of the plate; the middle spine is 

 intermediate in size and position. There is no suboral spine. None of the 

 spines are sacculate. Color, both above and below, pale yellowish. 



Station 4672. Peru: southwest of Palominos Light House, 88 miles, 2,84.5 fms. Bott. temp. 35.2°. 

 Fne. dk. br. infas. m. 



One specimen. 



' T/otds = tliree, in reference to the armature of the oral plates. 



