REPORT ON THE ASTEROIDEA. 517 



Depth 1375 fathoms. Globigerina ooze. Bottom temperature 35" '5 Fahr. ; surface 

 temperature 62° - 5 Fahr. 



Remarks. — This species may be recognised by the remarkably uniform character of 

 the small rounded elevations on the supradorsal membrane, and by the great number and 

 regular arrangement of the spiracula. The armature of the adambulacral plates and of 

 the mouth-plates also furnish conspicuous features by which the species may be distin- 

 guished. 



16. Hymenaster graniferus, Sladen (PI. XC. figs. 1 and 2 ; PI. XCI. figs. 7-9). 

 Hymenaster graniferus, Sladen, 1882, Journ. Linn. Soc. Lond. (Zool.), vol. xvi. p. 233. 



Marginal contour almost pentagonal, the interbrachial arcs being very slightly in- 

 curved. The rays are more or less attenuated or produced at the extremity, which is 

 upturned ; and their effect on the contour is consequently inconspicuous. Minor radial 

 proportion about 69 to 73 per cent. R = 30 mm. ; r= 22 mm. The radial areas are not 

 specially defined externally from the rest of the abactinal surface. Lateral fringe or web 

 thickened at the margin and little conspicuous. 



The supradorsal membrane is delicate. The paxillse-spinelets, which are delicate, and 

 have fine sharp extremities protruding well through the supradorsal membrane, are evenly 

 distributed over the area, but present no definite pattern of arrangement. The fibrous 

 bands, which are rather thin but clearly defined, are comparatively few in number, well 

 isolated, and radiate not only to those spinelets which form the immediate circle, but 

 some also pass through the interspaces and reach to the spinelets beyond. In this manner 

 a more or less irregular and very open network is produced, in which, however, a tendency 

 to an interpenetrant hexagonal pattern is discernible as the general plan here and there ; 

 and the whole is overlaid by a very delicate semitrausparent membrane, in which a number 

 of small, round, closely placed granule-like bodies occur. The spiracula are small and 

 sporadically placed ; very frequently two or even three occur together in the mesh, but 

 the groups are well isolated, and the apertures by no means numerous. The oscular 

 orifice is large and closed with five regular valves which fit evenly together, each with 

 about a dozen spines, the innermost two being longest, and the others diminishing regu- 

 larly and gradually, the articulatory base beiug prominent. 



The ambulacral furrows, which are narrow, are much constricted towards the actino- 

 stome and at the extremity of the ray. The armature of the adambulacral plates con 

 sists of three acicular spinelets, which are unequal in length and rather short, placed 

 in line parallel to the median line of the furrow, excepting towards the extremity, 

 where the series becomes rather oblique. The aboral spine is almost abortive, and the 

 middle one less than the adoral spine of the trio ; this latter is invested with a widely 

 expanded sacculus, which makes the spine appear many times thicker than its companion 



