The holotype was described by Alder & Hancock in 1854 from Herm in the Channel Islands, but the nudibranch has since been detected in other parts of the British Isles.

[2] Native to the northeastern Atlantic Ocean, C. glaucoides is found on the coasts of the British Isles, the Channel Islands, France and Spain.

It occurs in the littoral zone on rocky coasts, under stones and boulders, and often in association with hydroids.

Its small size and creamy white colour provides camouflage while it is feeding on the pale-coloured eggs of teleost fish and cephalopods.

So rich and nourishing is its diet that the gut does not have an anal opening, presumably because the food produces so little residue;[4] however, the larval stage does have an anus.