REPORT ON THE ASTEROIDEA. sil 
The anal aperture is subcentral and large, but no modification occurs in the surround- 
ing paxillee. 
The madreporiform body is entirely obscured by paxille, a group of five or six larger 
than any of the others marking its position, which is rather nearer the marginal plates 
than midway between them and the centre of the disc. The madreporiform body is of 
large size ; and appearances lead to the inference that it is compound. 
The ambulacral tube-feet are conical, with a very small mamelon-like termination. 
Colour in alcohol, a bleached ashy white, rather darker and greyish on the paxillar area. 
Locality Station 343. South-west of the Island of Ascension. March 27, 1876: 
Lat. 8° 3’ 0” S., long. 14° 270” W. Depth 425 fathoms. Volcanic sand. Bottom tem- 
perature 40°°3 Fahr. ; surface temperature 80°'8 Fahr. 
Remarks.—This species is readily distinguished by its broad supero-marginal plates, 
and by the row of well-developed spinelets on the actinal surface of the adambulacral 
plates, immediately behind the furrow series; as well as by the incipient grouping of 
the outer granules on the actinal surface of the plate. 
3. Plutonaster rigidus, n. sp. (Pl. XIV. figs. 3 and 4; Pl. XV. figs. 3 and 4). 
Rays five R=80 mm.;7r=21mm. R<4,r. Breadth of a ray between the fourth 
and fifth supero-marginal plates, 16 mm. ; midway along the ray, 9°75 mm. 
Rays elongate and rather narrow, tapering from the base to the extremity. Inter- 
brachial arcs very open, with a wide well-rounded curvature. Rays depressed and fiat, 
lateral walls nearly equally rounded abactinally and actinally. Disk comparatively large. 
Abactinal and actinal surfaces subplane, the latter slightly prominent at the mouth-angles. 
Abactinal surface faintly carinate along the median radial line. The general form has 
consequently a flat appearance and is of nearly uniform thickness throughout, excepting 
towards the end of the rays. 
The abactinal surface of the disk and rays is covered with numerous, rather small, 
compact, closely crowded, uniform paxille. These bear on a low broad tabulum from ten to 
twenty papilliform granules, two to five or sometimes even more being central. Although 
closely crowded the individual paxillee may be more or less clearly distinguished. In the 
central region of the disk, along the median radial line, and upon the whole of the outer 
two-thirds of the rays, no order of arrangement is discernible. In the abactinal inter- 
radial areas, on a region adjacent to the marginal plates, the paxillee are disposed in lineal 
series, the lines of which if produced beyond the margin would meet at a point in the 
prolongation of the median interradial line. These series do not extend far along tlie 
basal portion of the ray, and gradually diminish in length as they recede from the median 
interradial line. 
The supero-marginal plates, thirty-one in number from the median interradial line to 
the extremity, are rather large, and form a conspicuous and well-rounded border to the 
