Pelvetia canaliculata is a dark olive green sea weed, becoming black and brittle as the fronds dry out. It has stalk divided into branches of uniform width, without a midrib and with a cartilaginous texture. It is irregularly dichotomously branched and the receptacles are forked at the tips. It has channels along the frond, with appearance of groove at its base. It can survive several days without being covered by the tide, therefore, it is not habitual to find them in tide pools. 

Source: PEREIRA, Leonel. Guia Ilustrado das Macroalgas. Imprensa da Univ. de Coimbra, 2009.