REPORT ON THE ASTEROIDEA., 137 
The madreporiform body is large and conspicuous, subcircular or oval in form, and 
situated in an interradium close up to the supero-marginal plates, and consequently 
adjacent to the cribriform organ. Sometimes it is subtriangular in contour, with 
the base directed to the margin, and the striz form lines sharply bent at an angle, 
running moré or less parallel with the sides of the triangle, the open angle being 
directed towards the base. 
Colour in alcohol, yellowish white, with a bluish-grey shade over the disk. The 
marginal plates and the actinal interradial areas have a peculiar glazed appearance, 
consequent on the character of the investing membrane. 
Individual Variation.—A very slight amount of difference may be noticed in a series 
of specimens in the height of the lateral wall of the ray; and in some specimens the 
marginal plates stand rather more vertical, and are less arched towards the abactinal 
surface. In some specimens the small conical spinelet or tubercle on the upper margin 
of the supero-marginal plates is more strongly developed than in others; and in other 
examples it is absent altogether from some plates here and there, perhaps owing to 
abrasion. In some examples a very minute thornlet may be seen occasionally on an 
intermediate plate here and there in the actinal interradial area. In one specimen a third 
spinelet is present on some of the adambulacral plates, usually about the middle of the 
ray or near the mouth. 
In some examples the rays are rather broader at the base than in others, and 
this is especially noticeable in a large example from Station 46; in others they are 
longer and more attenuate throughout. 
Locational Variation.—The specimens from Station 45 appear to be of a rather 
smaller size than those from other Stations; the rays also are narrower, and the small 
spinelet on the supero-marginal plates is slightly more delicate and spine-like than in 
specimens of the same size from Station 47. 
On the whole, however, [| am by no means certain that these slight modifications 
can be correctly ranked as locational variations in preference to individual variations; a 
much larger supply of material would be necessary to decide the point than I have 
had at my disposal. 
Young Phase.—The smallest example, unquestionably belonging to this species, that 
I have seen, measures R= 8 mm.; 7 = 4 mm., approximately ; and it already presents 
the characters of the adult in a remarkable manner. I have no hesitation in referring it 
to the species. The abactinal membrane is very thin, and the spiniferous spicules are 
confined to definite areas which traverse the interradial lines. The anal funnel is well 
developed. There are four supero-marginal and four infero-marginal plates, and traces 
of a small fifth plate are visible, the infero-marginal one being the most developed, and 
appears to be the first formed. The cribriform organs are large and conspicuous. The 
adambulacral plates bear two short conically pointed spinelets. The mouth-plates have 
(ZOOL. CHALL. EXP.—PART LI.—1887.) 18 
