242 MR. W. PERCY SLADEN ON THE 



long, aud arranged in regular series of single columns extending 

 from the i\iargin of the disk to the ambulacral furrow ; their 

 breadth diminishes somewhat as they approach the margin, and 

 consequently that of the column also. The adambulacral plates 

 join up to the infero-marginal plates along the whole length of 

 the free portion of the ray, and there is consequently no exten- 

 sion of the interbrachial area along the ray. The imbricating 

 plates bear a few widely-spaced miliary tubercles or large gra- 

 nules upon their surface, usually 4 or 5 to a plate, but • upon 

 which they have no definite arrangement. 



Colour, in alcohol, grey, the paxillar area being a much darker 

 shade, which shows a strong contrast with the greyish white of 

 the marginal plates. 



Station 237. Lat. 34° 37' N., long. 140° 32' E. Depth 1875 

 fms. ; bottom temperature 1°'7 C, ; mud. 



Htphalastee planus, n. sp. . 



Marginal contour stellato-pentagonoid. E-ays five, of moderate 

 length, and comparatively slender from the disk outwards. In- 

 terbrachial angle very wide, more or less flattened, giving a 

 strongly marked pentagonal aspect to the large disk. The lesser 

 radius is in the proportion of 42 per cent.; 5 = 35 millim., r=15 

 millim. Disk depressed and not higher than the supero-marginal 

 plates, although apparently capable of a slight inflation. 



Dorsal area covered with small, closely crowded paxillse, which 

 are limited to the disk proper and extend very slightly onto the 

 base of the rays, the median dorsal line of the ray being covered 

 with membrane beset with small squamiEorm plates. The paxillse 

 are small and composed of 4 to 6 short and comparatively robust 

 spinelets, and so closely placed as to almost give the appear- 

 ance to the disk of being coarsely granulated, when seen without 

 a magnifier. A prominent conical anal protuberance is present 

 in the centre of the disk. 



The marginal plates constitute the entire thickness of the 

 animal, and form a well-rounded margin to the disk. Along the 

 rays the supero-marginal plates of the opposite sides do not 

 meet, but are separated throughout the whole extent of the ray 

 by a median dorsal membranous area beset with squamae. The 

 rays are comparatively slender and well rounded, having a cylin- 

 drical appearance, and proceeding somewhat abruptly from the 

 angles of the disk. The supero-marginal plates are 10 or 11 in 



