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



furrow series of ten to twelve small, delicate, cylindrical spinelets, their delicacy giving them 

 an elongate appearance. These are situated on the margin of the angular project ion, andradiate 

 slightly apart, the length of the spines diminishing as they recede from the apex of the angle. 

 Two or three still smaller spines form a continuation of the marginal series on each side 

 on the surface of the plate. (2.) On the actinal surface of the plate are a number of small 

 spinelets, similar in size and character to the furrow series. Au oblique line of three to 

 five, running subparallel to the adoral side of the angular prominence, is nearly always 

 definitely formed, and sometimes a second line of fewer spines is discernible, converging 

 towards the inner extremity of this line, with sometimes one or more spines in the 

 included area, but usually the spines additional to the oblique line first mentioned are 

 more or less grouped and irregular in their disposition. All these spines diminish in 

 length as they recede from the furrow. Several of the adambulacral plates on the inner 

 half of the ray bear at their junction with the marginal plates one of the large pedicel - 

 larian apparatus about to be described presently. 



The mouth-plates are broad aud conspicuous, but only slightly convex. The inner free 

 margin of the united pair is subcircular in outline or even subparaboloid. The armature 

 consists of ten small, slightly compressed, obtusely rounded spinelets, on each plate. The 

 innermost one is much the longest and most robust, and is abruptly pointed ; the other 

 spinelets decrease as they recede from the mouth. There is consequently a pair of larger 

 mouth-spines at each mouth-angle directed horizontally over the actinostome parallel 

 to one another, the five pahs meeting at the centre of the orifice. The actinal sur- 

 face of the plate is covered with a number of very small, uniform, delicate, thornlike 

 papilliform spinelets, rather widely spaced, amongst which no order of arrangement is 

 distinguishable. 



The actinal intermediate (ventral) plates are not more than eight to ten in number in 

 each interradial area, and they bear a peculiar pedicellarian apparatus. This is situated on 

 the suture between two laterally adjacent plates, and consists of five or six short tapering- 

 compressed spinelets borne on each jjlate on the margin of a semicircular cavity, over which 

 they are directed so as to meet and interlock at their tips with the corresponding series of 

 the neighbouring plate. The outline of the apparatus is suboval, and the cavity contains in 

 most cases a pulpy mass, probably foreign matter. There are five of the organs in each of 

 the interradial areas, the median one and the next adjacent on each side being the largest ; 

 and from three to six similar organs may be present on isolated adambulacral plates on 

 each side of a ray, as noticed above. A few pseudo-pedicellarhe of similar appearance, 

 formed by the modified spinelets of adjacent paxillae, occur occasionally on the paxillar 

 area of the abactinal surface. 



The anal aperture is subcentral and distinct, and surrounded by a circlet of slightly 

 larger spinelets. 



The papulae are confined to a limited area at the base of each ray, but I am unable to 



