Family Description:
Most species are flattened and one to six cells thick. Many have veins or a midrib. Tetrasporangia are tetrahedrally divided and usually occur in sori. Cystocarps are embedded in the plant. Carpospores escape through an ostiole.

Species description:
Winged Rib is one of our favorite red algae, and it is also one of the easiest to identify. It is yellowish or pink to a deep purplish red, and grows up to 25 cm (about 10 in) tall, although specimens can sometimes be found that are twice that height. A prominent midrib up to 1 mm in diameter extends throughout, and sends off alternate branches with three to four orders of branching altogether. Along both sides of the midrib and its branches lies a delicate, filmy blade up to a total of 12 mm (0.5 in) in width. On close inspection, perhaps with a magnifying glass, you can see that the branches of the blades sprout directly from the midrib of the previous order of branching, with no intervening stipes or stipelike parts. This type of branching is quite unique. At the base of each individual is a small, discoidal holdfast, which anchors it to the rocks or floats upon which it is growing. The thin blade tends to erode near the holdfast, leaving the midrib exposed as a stipe at this one location.

Male and female gametophytes are separate individuals, with spermatangia scattered over the surfaces of the ultimate bladelets. The tetrasporangia, however, tend to be scattered near the midribs.v
This species is a spring ephemeral so one needs to make the effort to see it from April to June.

Source:  North Pacific Seaweeds