REPORT ON THE ASTEROIDEA. 325 
armature consists of a marginal series of about eight short, lamelliform spinelets, similar to, 
but larger than, those on the adambulacral plates, which increase in size as they proceed 
inward. On the actinal surface of each mouth-plate, near the inner end, is one spine- 
let, exactly similar in size and shape to the corresponding spinelets on the adambulacral 
plates. 
The actinal interradial areas are large and occupied by intermediate plates which are com- 
paratively large in size and few in number. All are slightly tumid and covered. with the 
uniform granulation and membrane already referred to. Each of the plates in the series 
next the adambulacral plates bears a number of small, two-lipped, valvate pedicellarie, 
similar to those in Anthenea, but uniform in height with the granulation; from three to 
seven are present on a plate and show no definite order of arrangement. A few of the 
other intermediate plates bear occasionally a similar but isolated pedicellaria, Not more 
than three series of intermediate plates, and perhaps a few supplementary ones, are 
present. 
The madreporiform body, which is large and elongately oval, is situated external to 
the basal plate. It is bounded laterally and outwardly by two large plates; and its outer 
end is rather nearer the centre than midway between that point and the margin. Its 
surface is marked with very fine striations, which radiate with more than usual regularity 
from the centre to the margin. 
The ambulacral tube-feet are large and have very large flat sucker-disks. 
The primary apical plates are easily distinguishable on the disk :—The dorso-central, 
the under-basals, and the basals, the last mentioned being especially conspicuous. When 
the madreporiform body is placed in the right anterior interradium the anal aperture is on 
the right posterior side of the dorso-central plate. 
Small, isolated, pincer-formed pedicellaris, with two rather coarse jaws, are present 
here and there on the abactinal plates, and occasionally on the infero-marginal plates in the 
interbrachial ares near the lateral spines. 
Colour in alcohol, a bleached yellowish white. 
Young Phase.—The smallest example collected by the Challenger which measures 
R= 85 mm., r = 25 mm., has only two lateral spines on each infero-marginal plate, and 
the longest of these measures about 7 mm. ‘This specimen has twenty supero-marginal 
plates, and in all other essential respects corresponds to the description given above, 
Locality.—Station 187. Booby Island, Torres Strait. September 9, 1874. Liat. 
10° 36’ 0” 8, long. 141° 55’ 0” KE. Depth 6 fathoms. Coral mud. Surface temperature 
77°°7 Fahr. 
Remarks.—This species is readily distinguished from all other species of Stellaster by 
the three large lateral spines, by the tumid marginal plates, by the character of the 
armature of the adambulacral plates, as well as that of the actinal intermediate plates. 
The character of the abactinal plates points to its close affinity with Gonvodiscus. 
