Colonial ascidian form large three dimensional elaborate folded hemi-spherical masses.
Surface free of foreign particles and epibonts.
Zooid arranges in elaborate system around a large common cloacal opening.
Colonies are firm and resilient, with spicules distributes within the test providing firmness and responsible for the white speckled appearance especially visible in darker pigmented colonies.
Spicules stellate with sharp rays.
Atrial opening may be short or long tube-like siphon depending on the position in the test.
Retractor muscle extends from the posterior of the thorax.
Branchial sac with 3 rows of 8-10 stigmata.
Large testis follicle is covered by 7-9 spiral coils of the sperm duct, male and female gonads develop consecutively.
Larvae may vary in size and has three adhesive papillae and a variable number (4-8 depending on the developmental stage) laterally ampullae.
Hartmeyer, R 1913 Zoologische,und antropologische Ergebnisse eine for schungsreiese im westlichen un zentralen, sudafrica : Tunicata.5:125-144
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