|Original drawing used by Pease when he described the species in 1871.|
(Pease, 1871) 
Elysia rufescens is a species of sea slug, a marine gastropod mollusc in the family Plakobranchidae. This sea slug resembles a nudibranch but is not classified in that order of gastropods, instead belonging to a closely related clade, Sacoglossa, the "sap-sucking" sea slugs. This species was first described by Pease from Tahiti in 1871.
Elysia rufescens is olive green with large white spots, often in a reticulated pattern, and grows to about 6 centimetres (2.4 in). The parapodia are somewhat convoluted and have dark blue edges and a submarginal orange line. The rhinophores are rolled and have blunt, greyish ends.