506 THE VOYAGE OF H.M.S. CHALLENGER. 



radiate from the tips of the spinelets and pass to those standing in close proximity around, 

 the bands crossing at various angles, overlying and underlying one another, and forming 

 an interlacing tissue rather than a truly reticulated structure. The spiracula, which are 

 moderately large, are irregularly placed and not numerous. The paxilke seldom have 

 more than three spinelets, which are usually aggregated close together and especially so 

 along the median line of the ray and at the extremity, forming a crown of small expansion. 

 Towards the disk the spinelets are more widely spaced ; and the paxillse, which form the 

 pseudo-sides of the ray, are disposed in a perfectly straight line, no stragglers encroaching 

 on the web or interradial area. 



The oscular aperture is large aud conspicuous ; the valves are regular and formed of 

 comparatively few spinelets, seldom more than a dozen in each. The outer margin of the 

 oscular ring is very strikingly marked out by short, prominently protruding, pointed 

 spinelets, excentrically directed, very regularly disposed, and from the tips of which the 

 membrane hangs in graceful folds. 



The ambulacral furrows are moderately broad, sublanceolate in outline, fairly uniform 

 in width except near the mouth where they are constricted, and along the outer fifth 

 where they taper rapidly up to the extremity. The armature of the adambulacral plates 

 consists of two short, acicular, pointed spinelets, covered with membrane which forms a 

 moderately developed terminal sacculus. In some specimens this appears to be much 

 more developed in the adoral spine of the pair than in the aboral, which seems frequently 

 to be smaller than the other. The aboral spine is also placed higher in the furrow than 

 the adoral. The aperture-papillae are large, and with their investment, broadly lanceolate 

 or acumino-spatulate in form. 



The mouth-plates are short and rather broad, the aboral prominence being blunt and 

 well rounded. Each plate bears two very short, robust, stumpy secondary or superficial 

 spines, the adoral one (which is placed forward on the plate) being shorter even than the 

 mouth-spines proper, but much more robust. The mouth-spines proper, which are four 

 or five in number on each plate, are rather long, fine, and nearly equal in length.. 



The actino-lateral spines are robust and well-spaced, the fourteenth or fifteenth from 

 the mouth being longest. None meet in the interradial median line, not even the longest, 

 the space being filled in with fleshy membrane. 



Colour in alcohol, dirty white in large specimens, greenish grey in those of smaller 

 size. 



Locality. — Station 235. Off Japan, south of Omae saki. June 4, 1875. Lat. 

 34° 7'0"N., long. 138° 0' 0"E. Depth 565 fathoms. Green mud. Bottom temperature 

 38°'l Fahr. ; surface temperature 73° - Fahr. 



Remarks. — Hymenaster glaucus may be readily distinguished by the conspicuously 

 defined radial areas raised in relief above the rest of the abactinal surface, by the paxillse 

 with three spinelets, and by the character of the supradorsal membrane. 



