Shell size to 21 mm; shell narrow, elongate, aperture comprising most of shell length. Surface smooth, except for incised lines at shell ends. Aperture broad, flaring anteriorly. Color yellow, white, red or rosy-brown with areas of lighter color. Living on sea-whips; the photos of the live simnia on 'branches' of the sea whip Leptogorgia virgulata were taken by Amy Tripp on Marco Island on March 27, 2014.