JAPANESE ASTEROIDEA : 115 



:ingle, aud form a coutiuiioiis series with the ambidacral spiues. The rudi- 

 ments of a secondary mouth-spine, represented by a tliorn-Hke granule, occur 

 on each plate near the median suture and at the highest portion of the keel. 

 " The interbrachial areas are triangular in outline, flat, extensive, and 

 covered with imbricating scales of more or less regularly symmetrical liexagonal 

 form. These j)lates are broader tlian long, and arranged in regular series of 

 single columns extending from the 2iiargin of the disk to the arabulacral 

 furrow; their breadth diminishes somewhat as they approach the margin, 

 and consequently that of the column also. The adambulacral i)ktes join up 

 to the infero-marginal j)lates along the whole length of the free iwrtion of 

 the ray, and there is consequently no extension of the interbracliial area 

 along the ray. The imbricating plates bear a few widely-spaced miliaiy 

 tubercles or large gi-anules upon their surface, usually 4 or 5 to a x^late, but 

 iTpon wliich they have no definite arrangement. 



" Colour, in alcohol, gi-ey, the paxillar area being a much darker shade, 

 wliich shows a strong contrast with the greyish white of tlie marginal plates. 

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

 bottom temperatm-e 1°.7 C; mud." 



Essentially the same description is reproduced in the full report of the 

 "Challenger," with a few additional observations, as may be seen from the 

 following [Sladen, '89, p. 162] : 



" Hyphalaster inermis, Sladen (PL XXV. figs. 4-6 ; PI. XXVm. figs. 5-8). 

 (Reference to the foregoing description.) 

 "Rays five. R=20mm.; r=8.5mm. R<2.5r. 



"Marginal contom- stellato-pentagonoid. Rays well developed, slender, 

 round, and tapering but slightly. The disk is depressed, not inflated, and 

 both the abactinal and actinal surfaces stand on a level with the edges of 

 the marginal plates. The minor radius is in the j)rox3ortion of 42.5 per cent. 

 The interbrachial arcs are very wide and expansive, the curve being slightly 

 flattened at the summit of the arc emphasises the marked pentagonal contoiur 

 of the body-disk. 



" The abactinal area is covered with closely crowded paxillœ, the whole 

 disk as well as the base of the rays being imiformly packed. The paxill^ 



