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° 22' 0" W. Depth 2335 fathoms. Red clay. Bottom temperature 

 34° - 8 Fahr. ; surface temperature 63° - Fahr. 



Remarks. — Hymenaster echinulatus is remarkable for the large peak-like prominences 

 formed by the paxillas-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, 18S2, Journ. Linn. Soc. Lond. (Zool.), vol. xvi. p. 220. 



Marginal contour substellate ; iuterbrachial arcs well defined, the minor radius in the 

 proportion of 592 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 paxillse-spinelets are 

 uniformly and closely distributed over the wdiole 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 spiiacula 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 regular 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 spiuelet 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 spiuelet itself. 

 The aperture-papillae are moderately large, elongate, and suboval. A fleshy thickening 



