232 MR. W. PERCY SLADEX OS THE 



become somewliat irregular as they approach the raouth-angle, 

 consequent on the increase in the size of the plates, which are 

 also more irregular in shape. A few small granules very widely 

 and irregularly placed occur on the plates here and there. 



Colour, in alcohol, greyish white, the paxillar area and the 

 cribriform organs having a slightly brownish tinge. 



Station 346. Lat. 2° 42' S., long. 14° 41' W. Depth 2350 

 fms. ; bottom temperature 0°'4 C. ; Glohigerina-ooze. 



Stybacaster armatus, n. sp. 



Eays five, long and slender, subcylindrical, nearly uniform in 

 tliickness throughout their length, the expansion at the base 

 and the attenuation at the tip being very slight. Interbracbial 

 angle very wide, with the curve somewhat flattened in conformity 

 with the pentagonal character of the disk. The lesser radius in 

 the proportion of 28 per cent, ; i2 = 38 millim., r=ll millim. Disk 

 depressed, not inflated, and not higher than the marginal plates. 

 Dorsal area covered, with a leathery integument beset with 

 minute imperfect pseudo-paxillse and simple spiculate spinelets 

 closely crowded, the general appearance being that of spinelets 

 only. Spaces at the base of the rays naked. JS^o definite 

 epiproctal protuberance, a faint indication of the centre only 

 present. 



Marginal plates high, curving inward slightly above and below, 

 and forming a rounded margin. The supero-marginal series are 

 9 in number from the median interradial line to the extremity, 

 exclusive of the terminal, and all are considerably longer than 

 high. Along the rays, commencing at the fourth plate from the 

 arm-angle, the supero-marginal plates of either side meet in the 

 median dorsal line and entirely encase the upper portion of the 

 ray. The ray is rather compressed laterally, and the dorsal 

 surface is arched. Each alternate supero-marginal plate along 

 the ray bears a large robust conical spine placed in the median 

 line of the ray, the series forming a single line of five spinelets, 

 which stand perpendicular to the ray and diminish in size as they 

 proceed outward. The longest spinelet remaining measures 

 about 6 millim., and the tip appears to have been broken. The 

 penultimate supero-marginal j)late is small, and the ray is slightly 

 bent upwards at the extremity. The terminal plate is small 

 and comparatively inconspicuous, not at all swollen or tubercular, 

 and is less than the pair of antepenultimate supero-marginal 



