Believed to contain only a single species, that is commonly called the Spanish Dancer, it is large, wide, flattened and soft bodied with a broad mantle skirt that is normally furled up over the edge of the dorsal surface of the body. This skirt is able to be unrolled revealing brightly coloured patches, thereby producing a startle display when disturbed (diematic behaviour).
They have peculiar, large, plate-shaped oral tentacles possessing papillae along the outer edge. The lamellate rhinophores are clubbed at the distal end and are able to contract into separate pockets.
There are six, separately inserted, compound gills on the posterior end of the dorsum forming a circle around the anus. These are contractible but are not able to be retracted into pockets below the mantle surface. They are able to swim with dorso-ventral flexions of the body combined with undulations of the unrolled mantle skirt presenting a flamboyant/startling display.
They have a wide tropical to sub-tropical distribution. Feed upon sponges.