342 BULLETIN 76, UNITED STATES NATIONAL MUSEUM. 



a trille; spinules decreasincr in lenj^th toward tip of ray, but increasing sliijlitly 

 toward margin. Papulae lonjr and conspicuous, tliree to seven to an area. The 

 spinules give a bristling appearance to the abactinal surface, and the membrane 

 connecting the spinules is frequently emarginated at their tips. The groups appear 

 distinctly spaced owing to the large meshes of the dorsal skeleton. Anal aper- 

 ture surrounded by a row of short obtuse spinelets, and to one side of it the flat 

 subcircular central plate may be seen in a dried specimen. 



Actinal surface paved with two longitudinal rows of band-hke plates, which 

 are comparatively wide and short: (1) the adambulacrals bordering the furrow, 

 and (2) external to them a series of equally regular plates, probably the inferomar- 

 ginals. Adambulacrals much wider than long and separated by prominent sutures; 

 each plate with a transverse series of three prominent spinules, sheathed individ- 

 ually in membrane, which extends beyond the tip in a short sacculus; each spinule 

 surmounting a slight boss on the plate, one situated on the furrow margin, another 

 on the extreme other margin, and one exactly midway between the two; inner 

 spinule 2 mm. long, and the other two successively slightly longer and stouter. 



Inferomarginal plates a trifle longer than adambulacrals and not quite so 

 wide, so that they do not exactly correspond to the latter, even though the sutures 

 are not so prominent. Surface of each plate actinal in position and slightly con- 

 vex, and the outer, lateral end bearing a prominent membrane-invested spinule, 

 3 to 3.5 mm. long, which superficially appears to stand in a linear series wnth the 

 adambulacral armature; inferomarginal spinules, of which about thirty-five can 

 be counted to the side of each ray, decreasing in size toward extremity, where 

 both marginal and adambulacral plates with their armature are very small; about 

 ten lateral cruciform plates immediately adjacent to (above) inferomarginals, 

 form perhaps the superomarginal series. 



Mouth plates very prominent actinally, the exposed surface rising toward 

 the median suture; the combined pair thus with a very prominent but rounded 

 beak about midway between inner and outer angles, or a little nearer the outer; 

 margin of each plate rounded, but somewhat angular where the furrow edge merges 

 with that turned toward the mouth; general form of mouth plates strongly re- 

 calling that of Pteraster and allied genera, the median beak on the actinostomial 

 margin, in line of the median suture, being present; armature consisting of four 

 marginal spinules, that nearest the mesial beak being largest, the third sit- 

 uated on angle between furrow and actinostomial margin at a lower level in the 

 furrow than the other spinules, and often directed across or down into the furrow, 

 wliile the others are reflexed ; fourth spine commonly standing somewhat on actinal 

 surface ; all enveloped in membrane, which is prolonged beyond the tip in a sacculus. 



Actinal interradial areas very small; apparently no actinal intermediate 

 plates. 



Madreporic body of medium size, situated about midway between center of 

 disk and margin, irregularly circular in outline, with coarse, often branching, cen- 

 trifugal ridges and narrower striations; anal opening somewhat eccentric, sur- 

 rounded by low, cylindrical, granuliform spinelets; ambulacral furrows wide; 

 actinostome not very wide, often completely close<l over by mouth plates; tube feet 

 in two series and with a button-like terminal disk. 



