Porphyra laciniata, the edible laver; Codium tomentosum, a coarse species; Padina pavonia, common in shallow water; Ulva latissima; Haliseris polypodioides; Sargassum bacciferum; the well-known gulf weed, probably transported from the Atlantic; Zostera marina, forming dense beds in muddy bays; the roots are cast up by storms and are valuable to dress the fields.
Some of these ancient seaweeds may have remained permanently rooted in the littoral regions, while others may have become broken off and drifted, like the recent Sargassum, at the mercy of the winds and currents, carrying the attached Graptolites into all latitudes.