STAEPISHES OF THE PHILIPPINE SEAS. 219 



half as long as the central. The groups are spaced 1 to 2 times 

 their diameter. The spines are much longer than the low tabulum. 

 The appearance is very similar to that of R. tisardi, there being shal- 

 low channels between consecutive transverse rows. From the coe- 

 lomic side the plates are seen to imbricate strongly in the transverse 

 series and slightly in respect to the plates on either side. 



Adambulacral spines 13 or 14, slender and pointed, in an upright 

 coordinated group and decreasing very rapidly in length from the 2 or 



3 on the furrow margin (equal to 1^ plates in length) to the 3 or 



4 small spinelets on outer edge of the group. In some groups an 

 arrangement in 4 longitudinal series is evident. The shape of the 

 groups is subcircular or roughly three-sided, and they are spaced from 

 one another about half the length of the plate. The tips of the 

 marginal spines are slightly compressed. 



Mouth plates narrow, densely covered with slender, tapering, 

 bluntly pointed, upright spines, which form a coordinated group for 

 each pair of plates. The outer margin of each plate has only a 

 slight angle between the furrow margin and that adjacent to the 

 first adambulacral. The marginal spines proper are 6 or 7, slender, 

 slightly flattened, bluntly pointed, the innermost the stoutest; 10 to 

 12 smaller spinelets continue this series to the outer end of the plate. 

 Another series of similar spinelets follows the margin of the suture 

 from the outer to inner end of plate, and an intermediate series is 

 present on the outer part of the plate. There are, in all, between 50 

 and 60 spines to each plate. 



Madreporic body large, Avith an irregular outline, and entirely 

 obscured by relatively very large paxillae. It is situated with the 

 inner edge about midway between center and margin. 



Gonads in a single tuft on either side of each membraneous inter- 

 brachial septum. Superambulacral ossicles, broadly elliptical in 

 form, are present. 



Young. — The young specimen from station 5605 has R 10 mm., 

 r 5.5 mm. The spinelets are extraordinarily delicate. The chief 

 difference between this specimen and the adult lies in the fewer and 

 T-elatively longer spines and the much lower tabulum of the mar- 

 ginal plates. The rays are, of course, relatively shorter and broader. 

 The paxillae have ordinarily 10 to 25 spinelets longer than the 

 tabulum. The spinelets of the marginal plates are very delicate and 

 in spaced groups on the middle of the convex plates. The proximal 

 inferomarginals have a low tabulum, scarcely half as long as the 

 spines, which are as long or longer than their plate. The terminal 

 plate is prominent and closely covered with delicate spinelets. Ac- 

 tinal intermediate plates in 3 chevrons; the spinelets long, delicate, in 

 spaced groups. Adambulacral groups of spinelets relatively a little 



