88 ]\rr. A. Alcock on 



broad border to the a})actirjal surface of the disk and rays. 

 Beyond them, when viewed abactinally, project the infero- 

 marginals for about one fiftli of their extent, so that from tliis 

 view the disk and rays have a double-festooned border — an 

 inner broad border formed by the supero -marginal ])lates, and 

 an outer narrower fringe formed by the uncovered projecting 

 ends of the infero- marginal plates. 



The infero-marginal plates correspond, plate to plate, with 

 the supero-marginals ; each carries on its projecting abactinad 

 end a tuft of enlarged spinelets, of which about three, usually 

 in an obliquely vertical row, are particularly large ; in the 

 interbrachial arcs, as far as the sixth plate, there are usually 

 from two to four additional enlarged spines in a vertical row 

 down the middle of each plate. 



The adambulacral plates are large and distant, each beara 

 a palmate furrow-series of about eight long needle-like 

 spinelets, and actinally a radiating rosette-like or paxilla-like 

 group of about twelve very much shorter spinelets. Except 

 that the mouth-plates are a little larger and have slightly 

 larger spines, they are not much moditied from the adambu- 

 lacral type. 



The actinal interradial areas are very large ; on the disk 

 each area carries about ninety strongly carinated plates 

 arranged in slightly oblique rows ; and on the rays similar 

 plates extend in a double series to about the tenth, and in a 

 single series to about the twentieth infero-marginal. In the 

 undenuded state each plate has the appearance of a very large 

 compact and beautifully expanded glomerular paxilla, owing 

 to the fact that the central carina of the plate bears a multi- 

 tude of stiff radiating spinelets arranged like the florets of a 

 composite flower. 



Madreporiform plate very large, entirely concealed by 

 enlarged paxillse, placed a little nearer to the margin tlian to 

 the centre. There is a central pore, anal in position, but 

 having, as is seen by dissection, no connexion with the gut. 



The tube-feet, which are in two rows, have a simple 

 papillary point. 



Andaman Sea, 250 fathoms. 



I beg to name this fine species after Mr. Percy Sladen. 



Family Pentagonasteridae. 



Pentagonastee, Linck, Sladen. 



21. Pentagonaster investigatoris, sp. n. 



E = l-6 r. R=82-5 millim. 



Disk pentagonal, much inflated in the radial, very concave 



