De Blainville, 1814
— Larva. Two types of veliger larva are distinguished: either with a single, left-coiled nautiloid shell, or with a simple inflated egg-shaped shell. An operculum is always present (contrary to the adult). The velum is simple and bilobed, and unpigmented. Paired statocysts always present, eyes may be present or not. The gut consists of a mouth, straight esophagus, a rounded stomach, two digestive diverticula (the left one always much larger than the right one), and a slightly twisted intestine. The kidney, if present, is unpigmented or slightly yellow. The retractor muscle is elongate and attached near or at the posterior end of the shell. Sizes approximately from 0.1 to 0.6 mm. Identification at the species level of the nudibranch veligers is not possible.
[After Hadfield, 1964]
— Adult. Shell and operculum absent in the adult phase. Calcareous spicules may be present in the skin; body-shape may be smooth and limaciform, aeolidifom (with dorso-lateral cerata), or flattened; if cerata are present, they may contain cnidosacs; head often bearing both oral and rhinophoral tentacles, the latter often wrinkled, lamellate, or branched, and sometimes retractable into elaborate pallial sheaths; mantle cavity absent; gill may take the form of a simple set of folds along the sides of the body, or may be a crescent or a ring of structurally complex contractile branchial appendages situated at the rear of the body; foot elongated, occasionally broad, closely united with the head and visceral mass; calcareous gizzard plates lacking, horny plates rare; potash-resistant jaws often present; radula very variable, uniseriate to broad, with or without the median tooth in each row; abraded or broken teeth are discarded, not retained in a special sac; pharynx sometimes with a muscular buccal pump; digestive gland compact, or much-divided, with tributaries from the head, foot, and cerata (where present); hermaphrodite reproductive system lacking an external seminal groove; penis sometimes armed with a stout stylet; impregnation never hypodermic; central nervous system euthyneurous, forming a ganglionic ring around the foregut. These are the true 'sea-slugs'.
[After Thompson, 1988]
The following 75 species of Nudibranchia occur in the area (De Kluijver et al., 2000a):