Generally very similar to Gammarellus homari . Posterior pereion segments, pleosome segments and urosome segment 1 with a dorsal keel; carinae less well developed than in Gammarellus homari and scarcely produced posteriorly; development of the keel variable. Coxal plates, epimeral plates, gnathopods, pereiopods and uropods similar to Gammarellus homari . Head with lateral lobes broadly truncated; eyes extremely large and occupying at least the half of the lateral surface of the head and not widely separated dorsally; eyes broadly oval. Telson slightly longer than broad, apex emarginate, with few apical and lateral spinules; telson rather longer in larger specimens.
Up to 15 mm, female larger than male.
Yellowish, mottled with reddish brown.
Typically intertidal or shallow subtidal.
North Atlantic and Arctic Ocean; American and European coasts; Baltic and North Sea. European coasts from northern Norway to Mediterranean.