270 THE VOYAGE OF H.M.S. CHALLENGER 



are six papulae round each tabulum, corresponding in position to the angles of the hexagon, 

 and they are separated from one another by the stellate prolongations between the plates. 

 The five primary interradial plates (basals) are clearly discernible and are distinctly larger 

 than any of the other tabula. They are all equidistant from the centre, being from four 

 to five times their own diameter distant. One bounds the adcentral side of the madre- 

 poriform body and is larger than the others. The dorso-central plate may also be 

 distinguished. 



The supero-marginal plates are fifteen in number, counting from the median interradial 

 line to the extremity. They form a conspicuous border to the abactinal area and their 

 breadth and length are subequal, except at the extremity, where they gradually diminish 

 in size, and the breadth is in excess of the length ; the plates are slightly convex and form 

 a bevelled edge to the paxillar area. Their surface is covered with small, low, truncate, 

 crowded granules, excepting a small irregular oval naked space on the abactinal surface. 

 A number of the plates bear one of the small excavate pedicellariae, similar to those 

 already described above, and these are frequently situated in the naked oval space. 



The infero-marginal plates correspond to the superior series, and are similarly covered 

 with small, low, crowded granules. Only five or six plates on each side of the median 

 interradial line have small naked areas on the actinal side, which are very much less 

 than those on the superior series and gradually diminish as they proceed along the ray. 

 It would appear that pedicellariae are normally not present on the infero-marginal plates. 

 In the example under notice I have only found one plate thus furnished. 



The adambulacral plates are a little broader than long, and their armature consists of 

 a marginal series of four or sometimes five short equal spinelets, irregularly cylindrical or 

 often more or less subprismatic. with roundly truncate tips, frequently subclavate, and on 

 the outer half of the ray more or less compressed in the direction of the axis of the ray. 

 At a short distance behind these are normally three low, thick, dumpy, subclavate, papil- 

 liform spinelets forming a slightly arched line traversing the plate diagonally, the aboral 

 end of the series being nearest the marginal or furrow spinelets. External to these are a 

 few (about five to seven) low, truncate, prismatic granules, which may either form two 

 subregular parallel lines, or a diagonal line subparallel with the second series of dumpy 

 papillae, with one or more granules filling in the vacant spaces at the corners left by the 

 obliquity of the line. These outer granules are scarcely distinguishable from those on the 

 adjacent actinal intermediate (ventral) plates to be described below. In two or three rare 

 instances an incipient pedicellaria is present on the adambulacral plates, but not more than 

 that number occur in the whole of the adambulacral plates of the example under description. 

 Pedicellaria; may therefore be said to be not present normally. Near the extremity of 

 the ray there are not more than three furrow spinelets on each plate, and finally only two. 

 And the second row of dumpy papilliform spinelets is at the same time represented by only 

 two, one of which is much larger than the other, and on the terminal seventeen or eighteen 



