502 THE VOYAGE OF H.M.S. CHALLENGER. 
bears two short, thick, dumpy, secondary or superficial spines. One near the adoral 
extremity, and the other, of similar size and character, standing behind it, about midway 
on the surface of the plate. There are four small, short, conical mouth-spines on the lateral 
margin of the plate, ranged serially above and behind the anterior pair of spines just 
mentioned, and interlocking with the corresponding spines of the neighbouring mouth-angle. 
The actino-lateral spines are numerous and very closely placed, the longest spine 
being far out upon the ray,—a much greater number being included within the inter- 
brachial are than usual. About forty spines stand on each side of the ray, the twentieth or 
twenty-first from the mouth being the longest. The spines within the disk are compara- 
tively short and uniform in length, and do not quite meet in the median interradial line ; 
muscular fibre, however, may frequently be seen underlying the outer tissue, passing from 
the tips of the actino-lateral spines to the corresponding ones of the neighbouring ray. In 
the immediate arm-angle, however, the spines are longer than the space between the angle 
and the furrow; so that a considerable overlap takes place, and a consequent puckering 
and deformity of the tissue ensues, which appears to develop frequently into an unsightly 
excrescence. The spinelets succeeding to the long ones decrease very rapidly in size towards 
the extremity of the ray. 
Colour in alcohol, brownish white or grey. 
Locality—Station 158. South of Australia, 1099 miles south-west of Cape Otway. 
March 7, 1874. Lat. 50° 1’ 0” S., long. 123° 4’0” E. Depth 1800 fathoms. Globi- 
gerina ooze. Bottom temperature 33°°5 Fahr.; surface temperature 45°-0 Fahr. 
Remarks.—This species may be distinguished from Hymenaster cxlatus, which it 
resembles in some respects, by the two large sacculated spines in the adambulacral arma- 
ture; and by the fact that the spiracula are confined to the interspaces between the raised 
areas of the paxillee-crowns, and are not distributed over the area of the crown as well, as 
in Hymenaster celatus. The colouration, the form of the aperture-papille, and the form 
of the mouth-plates are also different. 
5. Hymenaster echinulatus, Sladen (P]. LXXXIL figs. 1 and 2; Pl. LXX XIII. figs. 7-9). 
Hymenaster echinulatus, Sladen, 1882, Journ. Linn. Soc. Lond. (Zool.), vol. xvi. p. 218. 
Marginal contour pentagonoid. Interbrachial arcs moderately indented, the minor 
radius being in the proportion of 72°7 per cent. = 22mm.;7=16 mm. The rays are 
sharply tapered at the extremity, although when seen from above the angles of the 
pentagon have the appearance of being well rounded, in consequence of the outspreading 
and graceful curve of the marginal fringe; this is nipped together laterally at the 
extreme tip, and a slight upward continuation of the furrow is produced thereby. Form 
depressed, abactinal area slightly conoid, interradial spaces considerably sunken. 
The supradorsal membrane is thick and opaque, with very robust broad muscular 
