Colonies are think encrusting mats free of encrusting material or epibionts.
Colour of living specimens vary from cream, yellow, brownish to lilac.
Spicules are disk shaped and arranged around the zooid to form a capsule.
The spicule capsule is sometimes visible through the surface of the colony test.
The zooid (about 5 mm long) are arranges around the closely groups atrial opening in the centre.
Siphons are lobed with the atrial siphon forming a long tube.
Branchial sac has 4 rows of stigmata each with about 20 stigmata.
Larvae are about 1 mm long with 3 adhesive papillae with 4 fan shaped ampulla (distal parts fused) on each side.
Millar, R. H. 1962 Further descriptions of South African ascidians56:113-221
Monniot, C.; Monniot, F.; Griffiths, C. and Schleyer, M. 2001 Ascidians of South Africa.108:1-141
Shenkar, N.; Gittenberger, A.; Ruis, M.; Rocha, R. M.; Swalla, B.; et al. 2017 Ascidiacea World Database. Atriolum marinense Kott, 2001. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=250052 on 2019-03-12