Probably uncommon in the Solitary Islands Marine Park. Recorded from New South Wales, Victoria, Tasmania and the southern part of Western Australia.
Frequents rocky reef, intertidal and subtidal areas, where it feeds on sponges, possibly Clathria sp. Depth to at least 4 m.
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.
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.