REPORT ON THE ASTEROIDEA, 157 
The abactinal area is covered with a thin and almost transparent membrane, which 
is indurated with a great number of spiniferous spicules or pseudo-paxille. These 
consist of a circular scale-like base, from the centre of which a spine-like process rises 
vertically, and this may be divided into two, three, or four equal spinelets, the latter 
number being the most general in the centre of the disk, and those with one spinelet near 
the margin. The spinelets are moderately robust, obtuse, all united at the base, and 
radiating apart very slightly, have more or less the appearance of imperfect paxilla, 
whilst the squamous basal plate is scarcely larger than the diameter of the vertical 
spinous process. These pseudo-paxille are rather crowded in the immediate centre of 
the disk, but are elsewhere moderately and uniformly well-spaced. There are no papule. 
The presence of an actual anal aperture is doubtful. 
The marginal plates form a perpendicular wall of small but uniform ‘height. The 
upper margin of the superior series and the lower margin of the inferior series are slightly 
bent inwards and form bevelled edges. The supero-marginal plates are eight in number, 
counting from the median interradial line, exclusive of the terminal. The innermost 
plates are nearly twice as long as high, and the outermost are higher than long. The 
two innermost plates on each side of the median interradial line each bear a single, very 
minute, conical spinelet near the upper margin, and directed horizontally. The two 
outermost supero-marginal plates extend to the median radial line, where they join 
the corresponding plates from the other side of the ray ; the two next plates are separated 
by a narrow strip of the abactinal membrane with pseudo-paxille, and the remaining 
plates fall in the disk margin. The terminal plate is slightly tumid proximally, and 
tapers rapidly to a fine extremity, which is continued in a robust, sharply pointed, 
terminal spine. This spine, which is longer than the plate, is placed in the median radial 
line of the ray, and is directed outward and slightly upward from the horizontal; two 
smaller spinelets less than half the size of the above are placed at a lower level, one 
on each side of the extremity of the furrow. 
The infero-marginal plates correspond in number and breadth to their superior com- 
panions ; their height is less than the length, and varies very slightly throughout the ray. 
Seven cribriform organs are present in each interbrachial arc; they are very narrow, 
and the outermost are almost imperceptible. Their structure is papilliform. (See 
Pl. XXVIII.) 
The ambulacral furrows are narrow and entirely closed in by the overarching plates 
and spinelets. The adambulacral plates are large and subcrescentric in form, with the 
extremities truncate and the incurved margin directed towards the furrow. Their 
armature consists of three spines to each plate, which are moderately long, slightly 
tapering, obtuse, and rather compressed, covered with very delicate membrane, which 
near the base unites with that of the adjoining spines, and forms a rather broad con- 
tinuous web, by which the spines are bound together in continuous series. The spines 
