504 THE VOYAGE OF H.M.S. CHALLENGER. 
Colour in alcohol, light-brown above, pure white beneath. 
Locality.—Station 286. In the Mid-South Pacific, near the meridian of 135° W., 
approximately midway between Sydney and Valparaiso. October 16, 1875. Lat. 33° 
29’ 0” S., long. 133° 220” W. Depth 2335 fathoms. Red clay. Bottom temperature 
34°°8 Fahr.; surface temperature 63°°0 Fahr. 
Remarks.—Hymenaster echinulatus is remarkable for the large peak-like prominences 
formed by the paxille-spinelets elevating the supradorsal membrane; it is also distin- 
guished by the two large, often unequal spinelets in the adambulacral armature, and by 
the deeply festooned marginal fringe. 
6. Hymenaster carnosus, Sladen (Pl. LXXXVIII. figs. 1-5). 
Hymenaster carnosus, Sladen, 1882, Journ. Linn. Soe. Lond. (Zool.), vol. xvi. p. 220. 
Marginal contour substellate ; interbrachial ares well defined, the minor radius in the 
proportion of 59°2 per cent. R=103 mm.; r=60 mm. Rays tapering regularly to the 
extremity. Abactinal area slightly convex, rising somewhat conoid in the centre; rays 
rather roundly arched. Actinal area flat or convex. A narrow, thick, fleshy, conspicuous 
fringe surrounds the entire margin. 
The supradorsal membrane is thick, fleshy, and opaque. The paxillee-spinelets are 
uniformly and closely distributed over the whole area, protrude greatly, and are covered 
with membrane, which gives them the appearance of broad-based, robust, conical thorn- 
lets, about 3 or 4 mm. in height, springing from the general surface. They are very 
uniform in size; and no definite order of arrangement is perceptible, nor is it possible to 
distinguish the individual crowns to which the spinelets belong. A more or less homo- 
geneous muscular layer overspreads the whole area ; and no specialised bands or fibres are 
superficially apparent. The spiracula are quite microscopic, and confined to small round 
groups, containing two or more very closely crowded together, placed in the hollow inter- 
spaces between the spinelets, and the whole quite invisible to the naked eye. The oscular 
orifice, which is large, has broad valves, squarely truncate at the extremity and all webbed 
together, the prominent thorn-like spinelets above mentioned marking out a circle at 
their bases of attachment 24 mm. in diameter. 
The ambulacral furrows are wide (8°5 mm.), nearly uniform in breadth until near the 
extremity, where they gradually contract. The tube-feet are numerous and closely 
crowded, but maintain the resular biserial arrangement. The armature of the adam- 
bulacral plates consists of two long, needle-shaped spinelets, placed side by side, in line 
with the margin of the furrow, or the very slightest trace oblique. The adoral spinelet is 
somewhat the longer, and both are invested with an extensive saccular membrane 
extending beyond the extremity, often to a length equal to that of the spinelet itself. 
The aperture-papille are moderately large, elongate, and suboval. A fleshy thickening 
