REPORT ON THE ASTEROIDEA. 649 
with delicate membrane bearing a number of small pedicellarize; the position of the 
aboral spine is rather high in the furrow, over which it is directed at an angle of about 
45°, and at a right angle to the margin. The two actinal spines are very unequal in 
size, the smaller one, situated close to the aboral end of the plate and a little on the 
furrow side of the median longitudinal line, is about twice the length of the small inner 
spine or even rather more, but very much more robust, especially at the base, which is 
thick, and the shaft tapers to a pointed extremity; it is articulated on a small tubercle 
and is covered with delicate membrane bearing small pedicellarie. The adoral com- 
panion, which may be considered the true actinal spine, is large and robust, about 4 mm. 
in length, and is articulated on a tubercular eminence, midway between the extremities 
of the plate and a little on the outer side of its median longitudinal line. The shaft is 
thick, cylindrical, and in the eight or ten innermost spines flaring at the extremity, and 
with its surface marked with comparatively coarse striations, which have often a slightly 
twisted appearance, and is covered with delicate membrane crowded with pedicellarie. 
The lateral spine is long, robust, and tapering, similar in character to the large actinal 
spine. It is articulated on a prominent tubercle-like rudimentary infero-marginal plate 
ankylosed on the lateral side of the adambulacral plate, and is covered with delicate 
membrane with crowded pedicellariz. The lateral spines are quite remarkable for their 
robustness in relation to the small size of the disk. 
The actinostome is wide, 7°5 mm. in diameter, that of the disk being 12 mm. The 
mouth-plates are small but powerful, and are remarkable for the number and size of 
the mouth-spines they bear. On the margin of each plate are three small cylindrical 
spinelets, two of them in front but away from the median suture, well spaced, radiating 
apart, and directed horizontally over the buccal membrane, whilst the third is further 
back and directed across the entrance of the furrow. Behind these are three long 
robust spines, placed close to the margin, which should in reality be counted as secon- 
dary spines, although when seen from above they have the appearance of being the 
marginal mouth-spines, and quite mask the small spines just mentioned. The inner- 
most are the longest and reach to the centre of the actinostome, the pair being directed 
horizontally over the buccal membrane, parallel to one another. The other two spines 
are smaller and the outermost is the least, and they radiate outward from the foremost 
slightly and in increasing degree. The shafts of these large secondary mouth-spines are 
cylindrical, robust, tapering, coarsely striated, covered with delicate membrane crowded 
with pedicellarie, which, though small, are larger than any of those before mentioned. 
The armature of the first pair of adambulacral plates succeeding the mouth-plates is so 
placed as to appear to belong to the mouth-plate armature; it consists of two small 
spines one behind the other placed quite in the furrow, then a larger actinal spine which 
appears to belong to the series of the large secondary mouth-spines, and still more inward 
on the plate a much larger and more robust actinal spine, this with its companion on the 
(ZOOL. CHALL. EXP.—PART LI.— 1888.) 82 
