Distribution: Probably uncommon in the Solitary Islands Marine Park. Recorded from New South Wales, Victoria, Tasmania and the southern part of Western Australia.

Ecological Notes: Frequents rocky reef, intertidal and subtidal areas, where it feeds on sponges, possibly Clathria sp. Depth to at least 4 m.

Additional Notes: Specimen pictured found on intertidal rock platform. Colour variable but mostly brown to orange. Lays spiral orange/brown egg mass. Differs from the similar R. arbutus by having a transparent rhinophore stalk and a rhinophore club which is translucent and white with some brown patches. Specimen pictured about 10 mm long, grows to at least 16 mm.

References: Gary Cobb, David Mullins, Nudibranchs Encyclopedia, 2nd Edition, 2015. Publishers Thomas Slone, Masalai Press and Tim Hochgrebe, Underwater Australasia. p.190.

Australian Museum, Sea Slug Forum. http://www.seaslugforum.net/find/rostcalu. Accessed 27/09/2018.