ASTEROIDEA OF H.M.S. ' CHALLENGEE ' EXPEDITION. 245 



BENTHASTEIt PENICILLATUS, 11. Sp. 



Marginal contour stellato-pentagonoid ; interradial angles mode- 

 rately indented and ■well rounded. Minor radial proportion 65"2 

 per cent.; It = ll'o millim., r=7-5 millim. The radii taper 

 gradually, and their extremities are somewhat upturned. 



Supradorsal membrane exceedingly delicate and rudimentary, 

 appearing little more than a thin mucous film over the inter- 

 brachial areas, becoming, however, rather spongiform over the 

 rays. Pedicels of the paxillte very thin and delicate, bearing a 

 crown of extremely long, thin, needle-like spines seYen or eight 

 times the length of the pedicel ; about 20 spinelets in a crown on 

 the disk, and about half that number, or less, towards the extre- 

 mity of tlie rays. The spinelets are of tlie most delicate descrip- 

 tion, vitreous in appearance, trilaminate, the transverse section 

 representing three cylindrical rods placed together, instead of 

 three flattened laminae as in the ]Drevious species. The spinelets 

 are widened at th.eir proximal extremity into a condyloid articu- 

 tory base, all fitting close together*, 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 dorsal surface upon which the 

 paxHlse are borne are very delicate, the prolongations being 

 attenuated in 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 car- 

 ried out, that in the centre of the disk the whole of the dorsal 

 surface that can be seen under the oscular orifice is simply covered 

 with subcircular imbedded scales. 



The oscular orifice is very large. The valves (or their repre- 

 sentatives) consist of a compressed paxilla-crown composed of 

 rather more robust spinelets than the rest. The pedicels of these 

 modified paxillee are very mucli enlarged, compressed laterally, 

 and expanded at the top, upon which the spinelets are articulated 

 in a more or less regular double row, the pedicels standing in 

 the median radial line. Powerful muscular bands run between 

 the bases of the pedicels of the valves and form a regular pentagon, 

 near the centre of which the periproctal aperture is situate. 

 Close to the periproct and less than its own breadth away is 

 the remarkably small, round, insignificant, madreporiform body. 



