ASTEEOIDEA OF H.M.S. * OHALLEN&EE ' EXPEDITION. 237 



Colour, in alcohol, dark purple; the fibrous bands on the dorsal 

 surface being white, giving a very elegant effect. The suckers 

 very dark purple, almost black, with white tips. 



Station 218. Lat. 2° 33' S., long. 144° 4' E. Depth 1070 

 fms.; bottom temperature 2°"1 C. ; Glohigerina-oozQ. 



Htmenastee, membeanaceus, Wyville Thomson. 



Hymenaster membranaceus, Wyv. Thorns. (1877), Voy. of ' Challenger,' 

 Atlantic, vol. i. p. 108. 



Marginal contour subpentagonal ; interradial angles wide and 

 flat, the lesser radius in the proportion of 62 per cent, or less ; i2= 

 35 millim. approximately, r=22 millim. Eadii very narrow, and 

 tapering on their outer portions. Dorsal area almost flat, actinal 

 slightly convex, but deeply incurved along the median interbra- 

 chial lines. 



Supradorsal membrane thin and transparent, with a great num- 

 ber of fine muscular fibrous bands extended between the tips of the 

 paxillse-spinelets, passing from one to each of these in the vicinity 

 and crossing one another in all directions, but without merging 

 or forming a reticulated tissue in the true sense of the word.. 

 Tissue semitransparent, with a few isolated spiracula here and 

 there. The tips of the spinelets produce slight prominences 

 but there is no massing of the tissue or the fibres upon their 

 extremities, which are consequently quite sharp and little con- 

 spicuous. Oscular orifice very large, the outer or basal circum- 

 ference measuring 12"5 millim. in diameter. Each valve is com- 

 posed of at least ten radiating spines, their bases of articulation 

 forming a prominent semicircular boss in each radius. 



Ambulacral furrows narrow and deep, scarcely petaloid 

 although much narrower near the mouth and rapidly tapering 

 at the extremity ; adarnbulacral plates high Ambulacral spines 

 3, very short, stout, slightly tapering and slightly compressed, 

 placed high in the furrow, and each series standing in line 

 slightly oblique to the median line of the ray, and oblique also 

 to the horizontal plane of the furrow, the innermost spine being 

 highest up in the furrow and most aboral. Kot webbed. Aper- 

 ture-papillfe very large, covered with widely expanded membrane, 

 giving them a squarely oval or subquaclrate shape, often Avith a 

 slight peak. 



Mouth-plates rather small, sloping upward into the mouth, 

 aboral extremity tilted downward, prominent keel along the line 



