196 . MI{. \V. PERCY SLADEN ON THE 



dency towards quadruple arraugemeut. Ambulacral suckers mo- 

 derately long and slender, each comb having 3 to 4 (or occasionally 

 5) spinelets, the innermost not more than one third of the size 

 of the next spinelet, and placed in advance of, or aboral to, the 

 rest of the comb ; the outer spinelet usually rather longer than 

 the others. The web-membrane is semitransparent, moderately 

 indented, and, after passing from the outermost spinelet of the 

 comb, is attached to the web of the actino-lateral spine, slightly 

 in advance of the actino-lateral spine belonging to its own adam- 

 bulacral plate — the spinelet hanging right over the terminal piece 

 of web, which does not reach far out as in P. rugatiis. A rather 

 long saccular prolongation of the web-membrane occurs at the 

 tip of each of the ambulacral spines. Towards the extremity of 

 the rays the combs sometimes show a tendency to separate into 

 component spines, each being still clothed with membrane. The 

 aperture-papillae are somewhat jawbone-shaped, the thickened 

 extremity being directed adorally. ' 



The mouth-plates bear 4 to 5 spines on each side, long, and 

 stouter than the ambulacral spines, both series being webbed 

 together, the outer spine being sometimes very small and rudi- 

 mentary. The secondary superficial spines are small, not so long 

 as the innermost mouth-spines, but rather more robust. In one 

 or two plates of the specimen under notice there is a single irre- 

 gular secondary spinelet, smaller than and accompanying those 

 just referred to. The first ambulacral comb after the mouth- 

 plate series has its web continued on to the aboral extremity of 

 the mouth-plate ; hence these two combs meet. 



The actino-lateral spines are of moderate length and slender ; 

 the fringe extending a short distance free beyond the margin of 

 the test, and directed horizontally or in the plane of the ventral 

 svirface. 



Colour^ in alcohol, greyish white. 



Station, " off Marion Island." Depth 50 fms. 



Eetasteb, Perrier. 



Species enumerated. 



It. verrucosus, n. sp. I R. gibber, n. sp. 



R.peregrinator, n. sp. | .R. insignis, n. sp. 



EETASTEE TEERTJCOStJS, U. Sp. 



Marginal contour moderately indented in the interradia, which 



