Known throughout New South Wales, Australia, [with records from Eden, in the south, to Angourie in the north] and Victoria.
UPPER: Two-Fold Bay, New South Wales, 17mm long alive, March 1986
LOWER: Callala Point, Jervis Bay, New South Wales, 20mm long alive, November 1984. PHOTOS: Bill Rudman.
The colour pattern is somewhat variable but the head is usually reddish-brown with a white or translucent straw coloured streak up the midline between the rhinophores, and a streak on each side, which runs below the rhinophores and beneath the first ceratal cluster on each side. There is also a diamond-shaped patch, often outlined in white over the heart. A broken white line, runs back from the heart along the dorsal midline. The distal third of the oral tentacles have a yellow or whitish pigmentation while the rest is either red-brown or translucent in colour. There is often a whitish band, sometimes incomplete, halfway up the oral tentacles. The rhinophores can have 4 or 5 ridges or lamellae (see inset on upper photo), but in may specimens these are absent, apparently after regrowth of damaged rhinophores. Another character is that complete specimens uusually have a long tapering "tail" but this is often absent.
Interestingly, a high proportion of animals of this species have damaged "extremities" - rhinophores, oral tentacles and posterior end of foot. Perhaps living in the intertidal makes them more vulnerable to attack from predators, but if this was the single reason I would expect other intertidal species to show a similar level of damage.
• Angas, G.F. (1864). Description d'espèces nouvelles appartenant à plusieurs genres de Mollusques Nudibranches des environs de Port-Jackson (Nouvelles-Galles du Sud), accompagnée de dessins faits d'après nature. Journal de Conchyliologie, 12: 43-70
Rudman, W.B., 1999 (March 9) Phidiana newcombi (Angas, 1864). [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/phidnewc