^P. Baileyi.^ Frond three to six inches high, flat; branches emanate from edges of the flat stems; main branches wide-spreading and irregularly placed, secondary branches regular and alternate; branchlets one eighth to one half of an inch long, covered on the edges and around the top with incurved ramuli; branchlets broken off near the base of the branches in mature plants; branchlets usually uniform in length, but occasionally one is longer and branches like the primary stem; color black. Common on the California coast. ^P. Harveyi.^ Frond two to six inches high; grows in globose tufts, and has a bushy aspect; branches stiff and wide-spreading; stems and branches beset with simple or branched spine-like branchlets; color dark brown, or black when dry; does not collapse when taken from the water; cystocarps on short stalks; siphons four in number. It grows on eel-grass and algæ, and is common in Long Island Sound and northward. Called locally /niggerhair/. (Plate XXVI.) ^P. Olneyi^ (dough-balls). Fronds two to five inches high, densely tufted; soft filaments of hair-like fineness, much branched, and spreading; when in fruit covered with tiny balls or cystocarps; siphons four in number. It is common from Cape Cod to New York. ^P. fibrillosa.^ Frond four to ten inches high, rather robust below; main stem quickly lost in a number of prominent stems and spreading branches; irregularly and profusely branched, becoming ultimately very fine; numerous branchlets covered with colorless fibrils in hairy tufts, which give it a misty appearance; fibrils so delicate that they do not show well in dried specimens, but a distinct feature by which to recognize the species in the young plant; color light to dark brown; cystocarps adherent to branchlets or on short stalks; siphons four in number; main branches only corticated. It is common in summer on stones and on eel-grass, at low-water mark, from Cape Cod to New York. (Plate XXVII.) ^P. violacea.^ Fronds six to twenty-four inches high, pyramidal in general outline; main axis with long, wide-spreading branches at the base; branches rather robust and naked below, but numerous and becoming very fine and tufted at top; cystocarps adherent or on short stalks; siphons four in number; main stems corticated; ultimate branchlets show articulations; color brownish-red. It is common from New York northward. (Plate XXVII.) ^P. urceolata.^ Frond three to ten inches high; main stem bristle-like; branches naked below, divided and subdivided above; branches with short branchlets set at a wide angle and often recurved; siphons four in number; shows articulations; color deep red. Name refers to cystocarp, which resembles a pitcher. The plant grows in loose tufts, and is common from New York northward and on the California coast.