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



Simon's Bay, Cape of Good Hope. (Depth and conditions not recorded.) 

 Remarks. — This form is very nearly allied to the North-Atlantic species Psilaster 

 andromeda. It may be distinguished by the infero-margiual plates at the base of the 

 ray having three or four small flattened spinelets grouped in a slightly oblique series near 

 the aboral end of the lateral margin ; by the inner pair of mouth-spines being conspicuously 

 larger than the rest ; and by the supero-marginal plates not encroaching conspicuously on 

 the abactinal area on the outer part of the ray. 



3. Psilaster cassiope, n. sp. (PL XLI. figs. 1 and 2 ; PL VII. figs. 9 and 10). 



Pays five. R = 63 mm. ; r = 16 - 5 mm. R < 4 r. Breadth of a ray near the base 

 (between the third and fourth supero-marginal plates), 14 "5 mm. 



Rays elongate and tapering ; attenuate towards the extremity but with the breadth 

 diminishing very slightly along the inner half of the ray. Lateral walls rather high, well 

 and equally rounded towards the abactinal and actinal surfaces, but nearly straight and 

 vertical between these curves. Abactinal and actinal areas subplane, giving the rays a 

 more or less depressed conico-cylindrical form. Interbrachial arcs acutely but distinctly 

 rounded. 



The abactinal paxillar area of the disk and rays is covered with numerous small and 

 closely crowded paxillse. These are low and of uniform height throughout, and the larger 

 ones consist of ten to sixteen very short, thick, papilliform spinelets, with one to three 

 irregularly central, the whole forming a compact group, and looking more like rounded 

 granules than papillae. Excepting upon the central area of the disk, and along a narrow 

 band-like strip in the median dorsal line of the rays, the paxillse are arranged in very distinct 

 and conspicuous transverse series, each series distinctly spaced from its neighbours, and 

 with the paxillae slightly elongate in the direction of the axis of the ray. The paxillse 

 diminish slightly in size as they approach the margin, and also in the central area of the 

 disk. 



The supero-marginal plates, thirty in number from the median interradial line to the 

 extremity, form a broad and conspicuous border to the disk and rays. Midway along the 

 ray the breadth is subequal to that of the intermediate paxillar area, and the latter con- 

 tracts continuously up to the extremity ; the area is also at a slightly lower level than the 

 marginal plates, and this, together with the well-rounded curvature of the latter, gives an 

 emphatic character to the border. Except on the inner part of the ray the breadth is 

 greater than the height, and is considerably greater than the length throughout. The 

 abactinal and lateral planes of the plate are united by a full and well-rounded semicircular 

 curve. The two or three plates in the midst of the interbrachial arc are shorter and less 

 tumid in their curvature than the succeeding plates. The surface of the plates is covered 

 with rather large distinctly spaced granules, which become smaller, more crowded, and 



