REPORT ON THE ASTEROIDEA, 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 in 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 papille 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 papille ; 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, pomted 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 longer than broad, and with 
a slightly convex margin towards the furrow. Their armature consists of a furrow series 
of nine or ten-rather short, robust, subprismatic, 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. Hach 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 
papilliform, skin-covered spinelets, in which the longitudinal arrangement is often more or 
less disturbed and irregular in consequence of additional papillae; 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 papille ; 
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 shghtly as they 
proceed inwards. The actinal surface of the plates is covered with numerous small, 
low, skin-covered papille, which mcrease in size on the mner 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 papille are distinctly spaced, 
but no order of arrangement is distinguishable. 
(ZOOL, CHALL, EXP.—PART LI,—1887.) 14 
