Orchistoma collapsa

(Mayer, 1900)

With 16 radial canals in 4 groups of 4. Umbrella 7 mm wide and high, apex dome-shaped, side walls vertical; manubrium large; with large, prominent gastric peduncle; mouth with 8 slightly crenulated lips; gonads in proximal parts of radial canals; 16 well developed and 112 rudimentary tentacles, all with adaxial ocelli.

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