•*i48 THE VOYAGE OF H.M.S. CHALLENGER. 



being about 100 mm. measured from the resting plane. Rays well produced, rather 

 broad at the base and rather flat abactinally, tapering gradually to the extremity. The 

 interbrachial arcs very wide and well rounded. Aetinal area plane along the rays, con- 

 cave within the disk. 



The whole abactinal area is marked off by trabecular into large "regular triangular 

 papular areas, with a roundly conical tubercle at each angle. The tubercles fall into 

 regular longitudinal lines, forming a median radial line and two parallel lines on each side. 

 The tubercles or spinelets of the median line are not larger than the others, and all are 

 subequal upon the disk, the primary radial ones being only the slightest shade larger than 

 the others. The pentagon marked out by the primary radial tubercles is divided into 

 smaller triangles with tubercles at their angles, which causes the tubercles to appear 

 crowded there. From the base of the ray outward the tubercles diminish in size some- 

 what, and there is considerable irregularity in their distance apart. At the tip of the ray 

 they become robust, crowded, and more conical. Along the ray the papular areas are apt 

 to be irregular in form. There is a naked space devoid of tubercles and trabecular along 

 the margin of the disk, and this is rounded and rather tumid, so that the supero-margiual 

 tubercles are not normally visible along the margin of the disk and at the base of the 

 rays when the starfish is viewed from above. The granulation consists of small granules 

 with larger ones intermixed, the latter being more or less mammilliform, and often 

 showing a tendency to form groups which simulate indistinct little rosettes. A few small 

 elongate foraminal pedicellariar are present in each area, but are not numerous. The 

 trabecular are narrow, elevated, and well defined. The papular are numerous. The 

 granulation mounts the bases of the tubercles, but never covers the tip, terminating with 

 an abrupt line, which gives many of the tubercles rather an acorn-like appearance. 



The supero-marginal plates, which are twenty-seven in number from the median 

 interradial line to the extremity, are small and each bears a tubercle, which is rounded in 

 the disk area, but becomes more conical on the outer half of the ray, while the plate 

 which bears it is also more or less mammillated, the base of the tubercle spreading out 

 widely and occupying nearly the whole plate. 



The infero-marginal plates, which are twenty-nine or thirty in number, are confined 

 entirely to the aetinal surface, the supero-marginal plates forming the actual margin. 

 Each plate bears a similar tubercle, which may frequently be doubled, and sometimes 

 divided into three or four, all springing out of the one base. All the marginal tubercles 

 have non-granulated tips Like the tubercles on the abactinal surface. Elongate foraminal 

 pedicellariar are rather numerous on the infero-marginal plates, and are also present on 

 the superior series. In the space between the supero-marginal and infero-marginal 

 tubercles are a number of larger " granules," which bear a striking resemblance to paxillar 

 in consequence of having a circlet of smaller granules round their margin surrounding a 

 central granule. 



