(Forbes and Goodsir, 1851)
Up to 200-600 marginal tentacles, with basal abaxial spurs; ocelli present usually on each third or fifth tentacle. Umbrella, up to 37 mm wide, usually much smaller, flatter than hemispherical; mesoglea thin; manubrium quadrate, short, attached to subumbrella along arms of perradial cross; 4 long sinuous gonads along radial canals, contiguous with manubrium; with usually 1-2 spiral cirri (often lost upon preservation) and one cordylus between successive tentacles.