This species may reach a length of 10 mm. It is grey or green in colour, mottled with black. The rhinophores and the foot are paler. The swollen cerata are arranged dorso-laterally and may total up to twenty per individual. They are arranged in up to six rows, with one or two cerata in each half-row. The anal opening is antero-dorsal.
This sacoglossan has always been found in shallow water (but not on saltmarshes), perhaps its preferred habitat is among Zostera.
In Britain, it is exceedingly rare, with only four reports: two from Ireland, one from south west England, and one from the coast of Yorkshire (Distr. C. bellula). Elsewhere it has been recorded from Norway and through the Mediterranean Sea to the Black Sea coast of Bulgaria.