KEPOKT ON THE ASTEEOIDEA. 105 



apparatus, the position of which is usually near the aboral margin and not far from the 

 junction of the supero-marginal and infero-marginal series. 



The infero-marginal plates correspond exactly iu length to the superior series, but 

 their height is distinctly greater, appearing near the middle of the ray nearly twice as great 

 as that of the superior series. Within the interbrachial arc they form a broad border to 

 the actinal area of the disk, but this extent on the actinal area speedily diminishes along 

 the ray, where they are confined essentially to the lateral wall, and their curvature only 

 conforms to the rotundity of the ray. Their surface is covered with papillse similar to 

 those on the superior series. At the upper margin of normally every infero-marginal 

 plate, and close to the junction with the superior series, is a conspicuous pedicellaria, 

 formed of three or four enlarged and modified papillae ; the apparatus being larger and 

 more fully developed than those on the supero-marginal plates above noticed ; some- 

 times two are present on one plate. In the interbrachial arc about a dozen plates may 

 bear a single small, flattened, tapering, pointed spinelet immediately behind the pedicel- 

 laria, but so small that it is little more than an enlarged squamule. 



The adambulacral plates are large and massive, rather louger than broadband with 

 a slightly convex margin towards the furrow. Their armature consists of a furrow series 

 of nine or ten rather short, robust, subprismatie, skin-covered spinelets, equal in length, 

 excepting the outermost at each extremity, and standing parallel to one another and 

 erect, forming a nearly straight series. Each successive series is well-defined. On the 

 actinal surface of the plate, behind the furrow series, is a longitudinal series of about seven 

 shorter spinelets, well-spaced, covered with membrane, which gives them a more or less 

 strongly fusiform appearance ; and behind these again two or even three series of small 

 papilliforrn, skin-covered spinelets, in which the longitudinal arrangement is often more or 

 less disturbed and irregular in consequence of additional papillse ; the outer part of the 

 plate being well filled. At the aboral end of the line of the second series of spinelets on 

 the actinal surface is one large pedicellaria, formed of three or four large modified papillae ; 

 this apparatus is present on every plate, and forms a conspicuous object. 



The mouth-plates are large, elongate, prominent, and convex actinally. The outline 

 of the united pair somewhat resembles that of a classical spear-head, in consequence of an 

 angle at the junction of the free margin with the margin adjacent to the first true adam- 

 bulacral plate. Their armature consists of a marginal series of twelve to fifteen short, 

 erect, skin-covered spinelets on each plate, similar to, but smaller than, those on the adam- 

 bulacral plates, which are nearly subequal in length, or increase very slightly as they 

 proceed inwards. The actinal surface of the plates is covered with numerous small, 

 low, skin-covered papillse, which increase in size on the inner part of the plates, but 

 become quite small and granuliform on the outer part, especially towards the margin 

 opposite to the median suture. Though numerous these papillse are distinctly spaced, 

 but no order of arrangement is distinguishable. 



(ZOOL. CHALL. EXP. — PART LI. — 18S7.) 14 



