190 THE VOYAGE OF H.M.S. CHALLENGER. 
Station 49. South of Halifax, Nova Scotia. May 20, 1873. Lat. 43° 3’ 0” N., long. 
63° 39/0” W. Depth 85 fathoms. Gravel, stones. Bottom temperature 35°-0 Fahr. ; 
surface temperature 40°°5 Fahr. 
3. Leptoptychaster antarcticus, n. sp. (Pl. XXXI. figs. 3 and 4; Pl XXXII. figs. 7 
and 8). 
Rays five. R=15mm,r=6mm. R=25r, Breadth of a ray between the fourth 
and fifth marginal plates, 5 mm. 
Disk large and inflated ; rays short, broad at the base and thence tapering gradually 
to a sharply pointed extremity. Interbrachial ares wide and subparaboloid in outline. 
Abactinal surface of the disk convex and subject’ to more or less inflation; that of the 
rays subcarinate, with the character strongly marked at the extremity, but towards the 
disk gradually merging into the general tumidity, the inflation being sometimes empha- 
sised in spirit specimens by the presence of a slight depression along the median inter- 
radial line, probably consequent on the posture of the rays at death. Actinal surface 
plane. Lateral margin thin and rounded. 
The abactinal surface of the disk and rays is covered with very small and rather widely 
spaced paxille, consisting of twelve to fifteen or more extremely fine, short, delicate 
spinelets disposed ii a little tuft, but radiating more or less apart. No definite order of 
arrangement is discernible in the paxillee. 
The marginal plates are small and short. The superior series are very small; and 
have the appearance of being enlarged paxille rather than true marginal plates. They 
are confined entirely to the margin and the abactinal side ; and not infrequently the edge 
of the infero-marginal plates is also just visible when the animal is viewed from above. 
They bear a tuft of spinelets similar to, but slightly larger than, those on the true paxillas, 
and these are arranged on a well-developed eminence. They are devoid of any large 
spmes whatever. 
The infero-marginal plates are twenty-one in number, counting from the median inter- 
radial line to the extremity, and their breadth on the inner part of the ray is four or five 
times the length or even more, but diminishes as they proceed along the ray. They are 
well rounded at the margin and form a broad border to the actinal surface; their posture 
being very oblique in relation to the median radial line. Along the median line of each 
plate, that is to say, traversing its greatest dimension, is a high, narrow keel, which bears 
"a covering of small, delicate, uniform spinelets, slightly larger than those on the supero- 
marginal plates and abactinal paxille ; these are directed outwards and over the interven- 
ing channels between the keels. 
The adambulacral plates are small, with the length and breadth nearly equal. They 
bear an armature closely resembling that found in some species of Astropecten, which con- 
