REPORT ON THE ASTEROIDEA, 607 
The disk is small and depressed, with the abactinal surface plane and at a higher level 
than the base of the rays, the margin standing nearly vertical and being abruptly rounded 
at the junction with the abactinal surface. The whole abactinal surface is covered with 
minute, papilliform, skin-covered spinelets, all of uniform height, closely placed but dis- 
tinctly spaced. The membrane which covers the abactinal surface of the rays is very 
delicate and semitransparent. The inner portion of the ray, as far as the ovarial region 
extends, is furnished with transverse annular ridges, about twenty-three or twenty-four in 
number. ‘The ridges, which are equidistantly spaced and are opposite to alternate adam- 
bulacral plates, are very flexuous, and not unfrequently two neighbouring ridges on one 
side of the ray may be joined by a longitudinal prolongation in the median radial line and 
united to a single ridge on the opposite side of the ray, apparently corresponding to their 
interspace. ‘The ridges are very narrow and prominent, and are formed of minute imbri- 
cating ossicles, which bear very small, isolated, conical spinelets, the prominence of the 
ridges being greater and the spinelets much more widely spaced than in Brisinga ende- 
cacnemos. The abactinal membrane between the ridges bears narrow saccular bands 
crowded with minute pedicellariz, from one to three being present in each interspace. 
These traverse the ray from side to side or may be interrupted and irregular, and fre- 
quently conform to the flexure of the calcareous ridges. Minute spiniferous spicules are 
also present on the membrane of the ovarial region, and are most numerous at the sides 
of the ray and over the entire base between the disk and the ovarial inflation. Beyond 
the ovarial region the abactinal membrane is extremely delicate, and the saccular bands, 
which are broad and regular, are equally spaced and traverse the ray. 
The ambulacral furrow is wide and measures 3°5 mm. at a part where the ray is 7°5 
mm. (about 75 mm. from the disk). The adambulacral plates are longer than broad, 
measuring about 2 mm. at 75 mm. from the disk, and the furrow margin of the plate is 
rather deeply concave. The adambulacral armature consists of :—(1.) Two small spines on 
the furrow margin, one attached near the adoral end of the plate, which measures about 2 
mm., and the other near the aboral end, but being in the same line as the adoral spine is 
consequently not at the extremity of the plate. This spine measures 3°5mm. Both these 
spines are cylindrical, tapering, and covered with a delicate membrane bearing numerous 
small pedicellaria. (2.) On the actinal surface of the plate is an elongate, delicate, taper- 
ing spine measuring 8 to 9 mm., and invested with a membranous sheath, crowded with 
minute pedicellariz, which develops a short saccular extension at the extremity. 
The lateral spine at about 75 mm. from the disk is also about the same length, 8 to 9 
mm., or a shade longer. It is very delicate, and is similarly invested with a membranous 
sheath crowded with minute pedicellari. It is articulated on the lowest plate of the 
transverse annular ridge—a rudimentary infero-marginal plate—which is so intimately 
united with the adambulacral plate as to appear like a tubercular eminence of that plate. 
Further out on the ray the lateral spines are a little longer, but I have not found any 
