Redescription of - a ubiquitous intertidal hoplonemertean found along the West Coast of North America.

Stimpson, 1857, a barnacle predator, is one of the most common and conspicuous intertidal nemerteans found along the West Coast of North America from Alaska to California, but it is currently referred to by the wrong name. Briefly described without designation of type material or illustrations, the species was synonymized with the Atlantic look-alike, (Johnston, 1837) by Coe. Here we present morphological and molecular evidence that is distinct from . The two species exhibit differences in color of live specimens and egg size and are clearly differentiated with species delimitation analyses based on sequences of the partial regions of the 16S rRNA and cytochrome oxidase subunit I genes. In order to improve nomenclatural stability, we re-describe based on specimens from the southern coast of Oregon and discuss which species should be the type species of the genus. was one of the two species originally included in the genus Stimpson, 1857, but subsequent synonymization of with resulted in acceptance of the Atlantic species, , as the type species of the genus. We resurrect Stimpson, 1857 and following Corrêa's designation, this should be the type species of the genus .