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 paxille 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 aperture-papille 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 long in 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 actinal floor, 
is made up of very thickly packed, fine, delicate, crossing fibres. 
