Previously known only from southeastern Australia, but a recent message on the Forum [#23150] from Reunion Id, Indian Ocean, suggest that it is a widespread Indo-West Pacific species.
UPPER: Two adults, 'The Nursery', Jervis Bay, New South Wales, Australia, 15m on sand, March 1979. PHOTO: M. Scotland.
LOWER: 15mm animal, near Huskisson, Jervis Bay, sandy bottom, 8m, November 1984. PHOTO: Bill Rudman.
Animals up to 10mm are not uncommon in grab samples from sandy bays, but it is seldom seen alive. Clearly it spends its life buried in the sand, perhaps emerging at night. I have never seen large adult specimens, as illustrated in the top photo.
It is characterised by the two longitudinal brown lines on the cerata. In juveniles only the largest cerata have the brown lines, the smaller cerata being a uniform translucent brown colour.
• Burn, R.F. (1974). Notes on some benthonic opisthobranchs from Port Philip Bay, Victoria. Journ. Malac. Soc. Australasia, 3(1): 43-57
Rudman, W.B., 1999 (November 26) Cerberilla incola Burn, 1974.. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/cerbinco