ASTEROIDEA OP H.M.S. * CHALLENGER ' EXPEDITION. 235 



bj extremely delicate thread-like fibres, which form a regular 

 pattern upon the disk. Usually sis fibres proceed from the tip 

 of each paxilla-spinelet, and pass to the tips o£ the neighbourino- 

 spinelets ; and as these are all equidistant, it follows that a series 

 of regular interpenetrant liexagons is produced. The fibres are 

 all of uniform length, and do not cross over or under one another 

 as in H. ^uUatus. The spaces marked out or bounded by the 

 fibres form regular triangular meshes, and enclose several small 

 spiracula, generally 3 to 5. Sometimes the fibres are doubled, 

 and the tips of the spinelets protrude prominently. 



The valves of the oscular orifice are not conspicuous, the genera] 

 tissue of the dorsal area just described seeming to be continued 

 up to the extremities of the valves, whilst their bases of attach- 

 ment, which are usually well marked out by spinelets on promi- 

 nent bosses, are undistinguishable in the present example. 



Ambulacral furrows rather narrow, not petaloid. Ambulacral 

 spines 3, long and needle-shaped, placed in line parallel with the 

 median line of the ray ; the adoral spine longer than the breadth 

 of the furrow. 



Aperture-papillae of moderate size, subquadrate or rather elon- 

 gate in shape, when invested with membrane. 



Mouth-plates short, with wide lateral flanges ; the keel along 

 the lineof junction very prominent aborally. Mouth-spines 5 to 

 6 on each plate, moderately long and subaciculate, the middle one 

 longest; the innermost one ought perhaps to be ranked as a 

 secondary or superficial mouth-spine, although similar in form 

 and serial in position with the true mouth-spines. Midway on 

 the superficies of the plate and well away from the median keel 

 is a longer and slightly more robust secondary spinelet, similar 

 in character to the rest of the armature. 



Actino-lateral spines very wide apart, probably not more than 

 20 on a side, although the rays are so long, the 4th or 5th from 

 the mouth being longest ; these and the preceding spines, which 

 are included within the disk, all converge towards the interradial 

 angle, instead of running parallel to one another as in nearly all 

 the species of this genus. 



Station 286. Lat. 33° 29' S., long. 133° 22' ^Y. Depth 2335 

 fms. ; bottom temperature 0°-8 C. ; red clay. 



Htmenaster pullatus, n. sp. 



Marginal contour more decidedly stellate than pentagonoid. 



