220 THE VOYAGE OF H.M.S. CHALLENGER 



margin, which radiate outward slightly. There is a little diminution in the size of the 

 paxillae towards the centre of the disk, but no trace occurs of any epiproctal prominence 

 or peak whatever. The paxillae are arranged in very short transverse rows at the sides 

 of the rays, the irregular median space being wide. The paxillae become very small 

 towards the ends of the rays. 



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

 radial line to the extremity, are small, about as broad as high, and slightly tumid. They 

 are covered with papilliform granules, which are uniform in size and shape, and not very 

 closely placed ; and fine cilia are present in the furrows between successive plates. No 

 spines or tubercles of any kind are present on the supero-marginal plates. 



The infero-marginal plates are broader than high, the height being proportionately 

 greater than usual in the genus ; they do not extend beyond the level of the superior 

 series, and form a gently rounded curve towards the actinal surface. The lateral spines, 

 which are very small, short, taper, and slightly compressed, are four in number, placed 

 close together in an oblique line, passing from the adoral extremity of the marginal end 

 to the aboral side of the plate, the third from the margin being the longest ; the fourth 

 spine is usually rather shorter than the third, but sometimes equal. These spinelets, 

 though not closely appressed to the side of the ray, stand at an angle to the surface and 

 are directed somewhat upward and outward. Behind the line of lateral spines is a 

 line of small, flattened, spiniform squamules, larger than the general squamules of the 

 plates ; and on the in ner part of the ray one or two similar spinelets may be found on the 

 inner portion of the plate ; these, however, are wanting on the outer part of the ray, and 

 there is no definite line of spinelets on the aboral side of the plate. The surface of the 

 plate is covered with short papilliform spinelets rather than squamules, which become 

 longer, more delicate, and very numerous in the furrows. 



The armature of the adambulacral plates consists of delicate spines, of moderate length, 

 all cylindrical, and only slightly tapering, which form three regular series, with three 

 spinelets in each. The spines of the inner or furrow series radiate well apart, and the 

 middle one is the longest. The spinelets of the second series are all equal in length, and 

 slightly shorter than the inner series, and are frequently placed in a somewhat oblique line. 

 The spines of the outer series are, perhaps, a trifle smaller than the second series, and do 

 not always stand in a regular line ; sometimes an additional spinelet is present, and some- 

 times only two. 



The actinal intermediate plates are numerous, twenty to thirty being present in the 

 interradial area, each bearing about eight to ten short, delicate spinelets, rather widely 

 spaced, and radiating apart, which gives an appearance suggestive of paxillae ; and most 

 of the plates, excepting the inner series, have a long and more robust spinelet springing 

 from the midst. 



The mouth-plates, which are rather short and small, are covered with numerous closely 



