ASTEEOIDEA OF H.M.S. ' CHALLENGER ' EXPEDITION. 199 



innermost spine standing perpendicular, or even directed slightly 

 outwards. Hence, when seen from above, the smaller combs ap- 

 pear to have little more than one half, or at most two thirds, the 

 space of the larger combs. In the larger combs the innermost 

 spine is smaller and shorter than the rest, frequently not more 

 than half the length. In the smaller combs the innermost spine 

 is much smaller still, often quite aborted and apparently absent. 

 The other spines are nearly equal in length ; and both combs are 

 uniform with one another in this respect. The combs are thickly 

 webbed, and have large and elongate saccular extensions developed 

 over the extremities of the spinelets. 



Mouth-armature resembling that o£ H. verrucosus. Mouth- 

 spines 8 to 10 in number, 4 or 5 on each plate, both series 

 webbed together, forming a narrow scoop-like fan. Secondary 

 superficial mouth-spines, one on each plate, thin, cylindrical, 

 not tapering, no longer than the mouth-spines, covered with mem- 

 brane. 



Actino-lateral spines of moderate length, reaching up to the 

 margin of the test ; hidden in membrane, of which a saccular but 

 not indented prolongation extends beyond the extremities as a 

 fleshy marginal fringe. Segmental apertures of the dorsal 

 chamber very large and elongate, situated well within the trans- 

 verse combs, and quite hidden thereby. 



Colour, in alcohol, purplish grey. 



Station 149. Ofl:" Christmas Harbour, Kerguelen Islands. 

 Depth 120 fms. 



Retastek gibbee, n. sp. 



Marginal contour substellate, interradial angles acute, not 

 rounded. Minor radial proportion about 50 per cent. ; j5=28 

 millim., r=14 millim. Eadii 5, well rounded, tapering con- 

 tinuously from the angle to the extremity, with sides rounded, 

 tumid, and curving over on to the actinal area as in Ecliinaster. 

 Dorsal profile high, gibbous, rounded. On the actinal area the 

 mouth and surrounding portions are deeply sunken. 



Supradorsal membrane with reticulated fibrous bands, marking 

 it ofi" into square or rhomboid meshes of great regularity. In 

 the centre of each, 3 to 4 paxilla3-spinelet-tips are visible ; and 

 other spinelets radiate to the mesh-fibres, one (or occasionally 

 two) spiracula being situated in the interspaces. The white 

 fibres of the meshes form a conspicuous feature ; and the slightly 



LINN. JOTJEN. — ZOOLOaT, VOL. XVI. 14 



