REPORT ON THE ASTEROIDEA, 233 
extremity, form a broad and conspicuous margin to the disk and rays. ach plate is 
slightly tumid ; and midway along the ray their breadth is greater than that of the paxillar 
area, the latter contracting outwardly into a mere narrow strip. The length of the 
plates is about two-thirds of their breadth, and their height is about one-half the breadth. 
The abactinal and lateral areas of the plate are united by a well-rounded curve: the 
tumidity above mentioned being conspicuous there. The surface of the plates is covered 
with low, robust, granuliform papille, which become small and crowded in the regions of 
the transverse margins, there being a great disparity in size between these and the robust 
granule-like papilla along the median line of the plate. ‘his disparity, however, may 
vary in degree ; and sometimes one or more of the papilla on the tumidity or rounding 
are larger than the rest, and even simulate a small supero-marginal tubercle or low conical 
spinelet. The majority of the supero-marginal plates bear one or even two pedicellarice 
of simple formation, but each in relation with a pit in the plate, and frequently simulating 
very suggestively some of the foraminal or “excavate” forms of the organ found in the 
Pentagonasteridz and allied families. 
The infero-marginal plates correspond exactly to the superior series, and their breadth 
on the actinal area is as great as that of the superior series on the abactinal area. 
Their surface is covered with papillz, which become large, flattened, and squamiform in 
the median region of the plate towards the end adjacent to the adambulacral plates. Hach 
plate bears at the upper end on the aboral margin a slightly oblique row of three small, 
delicate, cylindrical, tapering spinelets, standing close together, subequal, rather longer 
than the plate, and appressed to the side of the ray. On the inner half of the ray there is 
frequently one or even two similar spinelets on the aboral margin of the plate between this 
series and the end of the plate adjacent to the adambulacral plates, but always widely 
separate. Sometimes four spinelets are present in the oblique lateral series, the upper- 
most being rather smaller than the others. 
The adambulacral plates are large and massive, rather longer than broad, and with a 
shghtly convex margin towards the furrow. Their armature consists of a furrow series of 
ten long, thin, very delicate, cylindrical spinelets, subequal in length, which is about 
equal to that of the plate, and standing subparallel. In a large example these spinelets 
are slightly compressed laterally, and all are covered with a very thin membrane. On the 
actinal surface of the plate are about three irrecular longitudinal rows of spinelets, with 
five or six in each, which are short, tapering, pointed, and covered with membrane, the 
whole forming a group rather than recular series. ‘The length of the spinelets on the 
actinal surface of the plate is much shorter than that of the furrow series, and diminishes 
as the spinelets recede from the furrow. 
The mouth-plates are elongate and narrow, and the united pair are subelliptical and 
prominent actinally. Their armature consists of a marginal series of very small, short, 
tapering, and rather widely spaced spinelets, which are closely appressed to the superficial 
(ZOOL. CHALL. EXP.—PART LI.—1888.) 30 
