314 THE VOYAGE OF H.M.S. CHALLENGER. 
Outward from the primary radial plate, the median radial line is occupied by a longi- 
tudinal series of hexagonal paxille, eight in number up to the base of the ray, the series 
being then continued along the ray in the form of rectangular plates, regularly square 
(excepting the first), against which the supero-marginal plates on each side of the ray 
abut. This series of plates measures about 1°5 mm. in breadth at the base of the ray, 
and 1 mm. midway between the centre of the disk and the extremity of the ray. Parallel 
to the median radial series of disk paxille are other longitudinal series of similar, but 
slightly smaller, hexagonal paxille, which diminish slightly in size as they approach the 
margin, their inner limit being the interradial line. The moderate-sized paxille are 
regularly hexagonal, with the margin beset with about twenty very short, subprismatic, 
truncate, papilliform spinelets, and having about seven to ten small uniform semiglobular 
granules rather widely spaced on the tabulum: the number varying a little according to 
the size of the plate. It should be noted, however, that the plates which occupy the 
depressed central area and its interradial extensions are more like plates than paxille, 
whilst those of the subinflated radial areas of the disk are distinctly paxilliform. The 
single series of small square plates which occupies the median abactinal line of the ray 
are covered with small semiglobular granules precisely similar to those on the supero- 
marginal plates, lineal marginal series being defined, especially on the lateral margins. 
The dorso-central plate is distinct and surrounded by a cycle of seven equal-sized 
plates ; this in turn is succeeded by a series of more numerous but less regular plates, 
amongst which the representatives of the under-basals must be sought. Some irregularity 
masks the easy recognition of the latter, but where they do appear regularly placed they 
are separated from the primary radial by a pair of plates. The basal plates appear to be 
smaller and less conspicuous than the primary radials and are nearly at the same distance 
from the centre. The madreporiform body is small and sunken, situated external to the 
adjacent basal. The anal aperture is external to the dorso-central plate. 
No pedicellarize of any kind are present. 
Colour in alcohol, ashy white on the marginal plates and on the depressed area of 
the disk ; whilst the inflated portion is of a very light brown shade, as are also the actinal 
interradial areas. 
Locality.—Station 192. In the Arafura Sea, between the Ki Islands and Banda Islands. 
September 26, 1874. Lat. 5° 49’ 15” S., long. 132° 14’ 15” E. Depth 140 fathoms. 
Blue mud. Surface temperature 82°:0 Fahr. 
2, Paragonaster cylindratus, n. sp. (Pl. LI. figs. 3 and 4; Pl. LIII. figs. 3 and 4). 
Rays five. R=51mm.; r=12'5 mm. R>4 7. Breadth of the ray midway between 
the centre and the extremity, 45 mm. 
Rays elongate, slender, narrow at the base, slightly tapering towards the extremity, 
