STARFISHES OF THE PHILIPPINE SEAS, 485 



carinals and superomarginals which overlap them. In the present 

 genus just the reverse is the case. The adradials are large and rest 

 upon the superomarginals and carinals. In the arrangement of the 

 dorsal skeleton Pholidaster and Cnemidaster are in essential agree- 

 ment with Zoroaster. 



BYTHIOLOPHUS ACANTHINUS Fisher. 



Plate 135, figs. 1, lo-c; plate 139, figs. 1, 2. 

 Dythiolophus acanthmns Fisher, 1916&. p. 31. 



Diagnosis. — Rays 5. R=:105 mm., r=13 mm. R=:8 r; breadth of 

 ray at base, 14 mm. Rays 4-sided, very gradually tapering ; abactinal 

 surface of ray sunken along median line except near tip, where the 

 surface is nearly plane; sides forming a steep bevel; interbrachial 

 arcs angular; radial plates sunken, but tumid, with a short, sharp 

 appressed spine; adradial plates prominent, forming margin of 

 abactinal surface, larger and smaller alternating, the larger and some 

 of the smaller with a central spine similar to the carinal spines; 6 

 lateral series of plates, each with a prominent central spine, the 

 third and fourth from top the longest; prominent adambulacral 

 plates with transverse series of 4 pines, and about 3 spinelets (on 

 actinal surface), the inner with 1 to several pedicellariae. 



D escriytion. — Disk distorted, but apparently subplane abactinally, 

 like the rays. The primary plates are not especially prominent. 

 Disk plates with a central, short, sharp, lanceolate spinelet 1.5 mm. 

 long, borne on a well-marked boss or mgimelon. General surface of 

 all plates of disk and rays covered with slender sharp membrane- 

 invested spinelets about 1 mm. long and spaced one-third to one-half 

 their length. On the disk they are a little stouter and the mem- 

 brane a little thicker than on the rays. Three or 4 stout, broadly 

 lanceolate pedicellariae surrounding each papula of the disk. 



Rays 4-sided, the side walls forming a steep bevel with abruptly 

 rounded upper and lower margins. Carinal plates tumid, broader 

 than long, overlapped by either adradial series, the plates of which 

 are much more prominent and decidedly broader than the exposed 

 portion of the carinals and form the margin of a shallow sulcus, at 

 the bottom of which are the tumid carinals. These adradial plates 

 are much broader than long and are of two sorts, larger and smaller 

 alternating (with some irregularities), the larger being roughly 

 lozenge-shaped or elliptical, the smaller irregularly elliptical and 

 wedged betAveen the outer half or two-thirds of a couple of larger 

 plates. Opposite the inner end of a small plate is a large papular 

 pore, there being thus a series along either side of the carinal plates. 

 Between the adradial and adambulacral plates are 6 regular longi- 

 13434— Bull. 100—19 32 



