REPORT ON THE ASTEROIDEA. 503 



fibrous bands, closely but irregularly reticulated, the interspaces being small, usually 

 oval, and each occupied by a single spiraculum. The paxillse are rather widely spaced, 

 the tips of the spinelets forming prominent little conical peaks or elevations of the mem- 

 brane, which on certain parts of the area conform themselves to a regular definite order of 

 arrangement. A regular curved row or ridge of these spinelets stands on each side of the 

 median line of the ray, forming a petaloid elevated area, which corresponds with the 

 position of the underlying ray, and imparts a very characteristic facies to the species. A 

 prominent circle surrounds the oscular orifice, marking out in a subpentagonal outline the 

 place of the attachment of the valve-spines. The oscular valves are five in number, com- 

 posed of rather short radiating spines, forming regular triangular fans, the web which unites 

 them being reticulated in a similar manner to the rest of the supradorsal membrane, the 

 valves when closed forming a prominent pyramidal peak in the centre of the disk. The 

 reticulated supradorsal membrane reaches close up to the margin of the lateral fringe. 



The ambulacral furrows are distinctly petaloid. The armature of the adambulacral 

 plates consists of two rather short spines placed side by side well up in the furrow, and 

 forming a straight line parallel thereto. The spines of a pair radiate slightly apart 

 from one another in the plane of their position, and each is covered with a thick semi- 

 transparent membrane which is somewhat expanded opposite the outer third of the spine, 

 imparting thereby an elongate subspatulate form, the adoral spine of a pair having a more 

 robust appearance than its companion. The aperturc-papillse are small and short, suboval 

 in form on the inner portion of the ray, but becoming more elongate as they recede from 

 the mouth. 



The mouth-plates are small, with a strongly developed ridge at the line of junction, 

 and a prominent peak aborally. Each plate bears two short, robust, conical secondary 

 surface-spines, one placed near the adoral extremity, and the other about midway along 

 the ridge ; both spines are nearly equal in length, not longer than the spines of the 

 adambulacral armature, very wide at the base, and tapering to a blunt extremity, faintly 

 bowed outward and the tip approximated to the tip of the corresponding spine on the 

 companion plate. There are three small mouth-spines ; two situated at the extreme outer 

 portion of the lateral margin, and one more inward. 



The actino-lateral spines are about twenty-four in number on each side, the eighth or 

 ninth from the mouth being longest. The spines anterior to this are included within the 

 disk, their extremities reaching almost but not quite up to the median interradial line. 

 The succeeding spines diminish in length gradually as they proceed outward, and even 

 towards the extremities remain comparatively loner m comparison with those of the other 

 members of the genus. The actino-lateral spines are very robust and taper slightly to 

 the tips, which project well beyond the membrane, and give the appearance of a sharply 

 indented margin. The web of the actino-lateral spines, which also forms the actiual floor, 

 is made up of very thickly packed, fine, delicate, crossing fibres. 



