44 THE VOYAGE OF H.M.S. CHALLENGER. 



rays flat and level. Actinal surface of disk very prominent at the mouth-angles, and 

 sloping thence to the margin and along the rays. 



The paxillae of the abactinal area are moderately large, numerous, and usually well- 

 defined, consisting of eight to twelve small, uniform, papillose spinelets, encircling a central, 

 robust, more or less elongate, conical spinelet. Smaller paxillse of three to five spinelets, 

 and without a central conical spine, are interspersed occasionally amongst the larger 

 paxilla3, and entirely occupy the outer part of the ray. Peculiar pedicellaria-like bodies 

 formed of four or five flattened and modified spines are present here and there, most 

 frequently along the margins of the abactinal area of the rays, where they form a more or 

 less definite line close up to the marginal plates ; and comparatively few are to be found 

 upon the disk, excepting in the neighbourhood of the papular areas at the base of the rays. 



The marginal plates are small, and confined to the side of the ray, to which they form 

 a nearly vertical wall. The supero-marginal plates are about thirty in number from the 

 median interradial line to the extremity ; they are longer than high, and little more than 

 the thickness of the plate is visible on the abactinal surface. Each supero-marginal plate 

 bears on, or near, this upper margin a moderately long conical spine, robust at the base, 

 tapering to a sharp point, and directed almost vertically. Two or three spines on each side 

 of the median interradial line are very small, then follow the longest spines on the ray, and 

 the series diminishes gradually towards the extremity. In consequence of the length of the 

 supero-marginal plates the spines are rather widely spaced. The general spinulation of the 

 plate consists of minute conical granules, widely spaced. Below the spine the plate is usually 

 very sparsely granulated, and not unfrequently a more or less extensive naked area occurs 

 at the base of the spine, only a few well-spaced conical granules being present at the sides 

 of the plate near the suture, except in the interbrachial arc, where the granules in- 

 variably extend over the whole of the plate. One of the four-valved pedicellarise may be 

 present on the suture between the supero-marginal plates, and sometimes two or three, or 

 more, occur in close succession in the interbrachial arc. 



The infero-marginal plates correspond to the superior series, each bearing a similar 

 and equal-sized conical spinelet, directed horizontally and placed opposite to the supero- 

 marginal spine. On the inner portion of the ray there may be one or two small spines at 

 the base of the lateral spine. The superficial spinulation of the infero-marginal plates 

 consists of conical or papilliform granules similar to those on the superior series, and some- 

 times a similar naked or sparsely granulated area occurs below the spine. On the edge of 

 these plates adjacent to the adambulacral plates are a series of pedicellarise of the same 

 form as those above described on the abactinal surface, but rather irregular in their 

 disposition. 



The adambulacral plates form an angular prominence into the furrow, and bear on 

 their inner margin a semicircular comb of about seven short, equal-sized spines, which 

 taper slightly, but are rather obtuse. External to these, on the actinal surface of the plate, 



