REPORT ON THE ASTEROIDEA, 529 
2. Benthaster penicillatus, Sladen (Pl. XCIV. figs. 6-9). 
Benthaster penicillatus, Sladen, 1882, Journ. Linn. Soc. Lond. (Zool.), vol. xvi. p. 245, 
Marginal contour stellato-pentagonoid; interbrachial arcs moderately indented and 
well rounded. Minor radial proportion 65:2 percent. R=11:°5mm.; r=7'5 mm. The 
rays taper gradually, and their extremities are somewhat upturned. 
The supradorsal membrane is exceedingly delicate and rudimentary, appearing little 
more than a thin mucous film over the interradial areas, becoming, however, rather 
spongiform over the rays. The pedicles of the paxil: are very thin and delicate, bearing 
a crown of extremely long, thin, needle-like spines, seven or eight times the length of the 
pedicle; there are about twenty spinelets in a crown on the disk, and about half that 
number, or less, towards the extremities of the rays. The spinelets are of the most delicate 
description, vitreous in appearance, trilaminate, the transverse section representing three 
cylindrical rods placed together, instead of three flattened lamin, as in the preceding 
species, The spinelets are widened at their proximal extremity into a condyloid articula- 
tory base, all fitting close together, and each moulded to the form of its fellows, the whole 
forming a compact basement to the crown. The spinelets constituting a crown expand 
very slightly apart, and protrude the greater portion of their length free and naked 
through the supradorsal membrane. 
_ The cruciform ossicles of the abactinal surface, upon which the paxille are borne, are 
very delicate, the prolongations being attenuated to a remarkable degree, here and there 
almost aborted, and the central portion of the ossicle manifesting a tendency to become 
rotund and squamiform. ‘This modification is so far carried out, that in the centre of 
the disk the whole of the abactinal surface that can be seen under the oscular orifice is 
simply covered with subcircular scales. 
The oscular orifice is very large. The valves (or their representatives) consist of a 
compressed paxilla-crown composed of rather more robust spinelets than the rest. The 
pedicles of these modified paxille are very much enlarged, compressed laterally, and 
expanded at the top, upon which the spinelets are articulated in a more or less regular 
double row, the pedicles standing in the median radial line. Powerful muscular bands 
run between the bases of the pedicles of the valves and form a regular pentagon, near the 
centre of which the anal aperture is situated. Close to the periproct and less than 
its own breadth away is the remarkably small, round, insignificant, madreporiform body. 
The papule are simple round sacs, as broad as long, and immensely large in proportion to 
the pedicles by which they stand. 
Supero-marginal plates are present at the extremity of the ray, and form a terminal 
arch or ocular guard; but they are not half the length of the similar pieces in the pre- 
ceding species. 
The ambulacral furrows are wide, not petaloid, and the margins of the furrow are 
very narrow. The armature of the adambulacral plates consists of two or three spines 
(ZOOL. CHALL, EXP.—PART LI.—1888.) 67 
