Rhodymenia delicatula is a small (15-22 mm) red alga, with flat leaf-like blades rising from a prostrate stolon, The blades start out as elongate ellipsoids, and can branch dichotomously once. or twice. Colors range from rose red to dark red. It grows in rocky crevices, in the lower intertidal and shallow subtidal. In the Eastern Atlantic, it is known from Britain to Spain, Morocco, and the Mediterranean. In the Northwest Atlantic, it is known only from Woods Hole, Massachusetts, where it was first collected in 1978. Likely vectors are ballast water and fouling. It s probably more widespread but is easily overlooked.