STARFISHES OF THE PHILIPPINE SEAS. 453 



ambulacral comb resembles the inferomarginal comb, and the arma- 

 ture of the adambulacrals closely resembles that of B. vannipes, except 

 that the furrow spines are slightly more numerous. The actinal sur- 

 face of the adambulacral plates is short and wide, the outer end 

 underlying the ventral swollen end of an inferomarginal, to which 

 the adambulacrals correspond in number. The surface midway be- 

 tween the outer and inner ends bears an oblique tumidity for the 

 reception of the subambulacral comb. The inner end of the plate 

 broadens fan- wise for the reception of the furrow comb. The sutures 

 between consecutive plates are actinally 2^ to 3 times the actinal 

 length of the plate at its most constricted part. 



Mouth plates prominent and strongly convex at the outer end. 

 Marginal spines 15 to IT, the 3 inner long, slender, pointed, and 

 directed over actinostome, the remainder usually standing upright 

 and much shorter and slenderer. They are united for about two- 

 thirds their length by a web which is continuous between the series 

 of companion plates. Near the inner end of the plate stands a 

 slender, sharp, prominent, suboral spine adjacent to median suture 

 and near its companion of the other plate ; 3 shorter spines stand on 

 the convexity near the outer end of plate midway between suture 

 and furrow margins. 



Madreporic body medium-sized, with 3 plates close to margin, and 

 situated at about the middle of r. 



Type.— Cut. No. 32649, U.S.N.M. 



Type-locality. — Station 5622, off Makyan Island, Molucca Islands, 

 275 fathoms, gray mud ; 1 specimen. 



Distribution. — Known only from the type-locality. 



Remarks. — Xenorias is more comparable to Rhipidaster than to 

 any other known genus, and the most important difference has been 

 indicated in the generic diagnosis. It may be well to mention other 

 differences, which are not necessarily generic. The abactinal skele- 

 ton of X. polyctenius has small meshes, with generally only 1 papula 

 to a mesh, while R. vannipes has a wide-meshed, reticulated skeleton, 

 with upward of 5, 6, or even more papulae to a mesh. In the latter 

 the plates bear a penicillate tuft of 4 or 5 prominent, sharp spinelets, 

 apparently free from thick membrane, while in polyctenius the spine- 

 lets are very small and are immersed in a common sheath. 



The marginal plates of Xenorias are peculiar in their orientation. 

 They are situated on the side of the ray and are oriented at an angle 

 of about 45° to its long axis, in such a way (pi. 133, fig. la) that the 

 inferomarginal forms a chevron with the superomarginal, pointing 

 toward base of ray. The free end of each plate is larger than that 

 meeting its fellow at the intermarginal line and bears the largest 

 spines. 



13434— Bull. 100—19 30 



