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“HYPHALASTER, n. gen.
Rays five, short, incapable of being reverted. Disk more or less depressed and pentagonal. Supero-marginal plates devoid of spines, sometimes uniting in the median dorsal line and enclosing the ray. Abactinal membrane with pseudo-paxillae; simple spinelets also present in some forms on the outer part of the area only. A conical epiproctal protuberance may be more or less defined in the centre of the disk, similar to that present in some species of Astropecten, but not developing the tubular structure of this appendage found in Porcellanaster. Actinal interradial areas extensive, paved with numerous thin plates arranged in regular columns and imbricating. Ambulacral furrows narrow and concealed. Ambulacral spines short, compressed, three to five in number, usually forming a kind of fan or independent series on each plate. Cribriform organs five to seven in number in each angle.”
(Sladen, 1883: 234)