Small, lower than hemispherical, with smooth surface and evenly circular coronal groove. Disc diameter recorded to 35 mm, height half the width, coronal groove prominent, circular (not crenate), delimiting central half of disc. Marginal lappets 16, with alternating 8 tentacles and 8 rhopalia in clefts between, shallow radial grooves in radii of lappets, delimiting gradually raised thickened radial pedalia. Tentacle clefts deeper than rhopalial ones. Circular muscle broader than in Nausithoe punctata, more than half lappet-length in radial extent. Gonads 8, contiguous in pairs, U-shaped initially, one arm of U growing outwards to underly circular muscle.
Coloration: endodermis chocolate-red throughout; mesoglea lightly yellowish-brown throughout; stomach walls deeply colored, as is mesoglea in lappets.
Nausithoe atlantica Broch, 1913, may be conspecific. (Provided figure is based on Nausithoe atlantica illustrations in Russell, 1970).
(After Russell, 1970; Larson, 1986).