The Anemones belonging to the fourth section, or tap-rooted actinia, have the base small, and terminating in a rounded point, and the body much elongated, as in _Edwardsia Calimorpha_ (Fig. 80), in which the body is non-adherent, somewhat worm-like, having the mouth and tentacula seated on a retractile column, the lower extremity inflated, membranous, and retractile. In the great family of the Actiniarians, Milne Edwards forms a special group of the Phyllactinæ. In this group the polyps are simple, fleshy, and present at once simple and composite tentacula. Such is _Phyllactis prætexta_ (Fig. 81), which is found in the neighbourhood of Rio Janeiro. The zoophyte fixes itself upon the rocks on the sea shore, and covers itself with sand. Its trunk, of cylindrical form, is of a flesh-colour, with vertical lines, having red points. The interior tentacles form two simple elongated rows; the exterior tentacles are spatulate and lobed, not very unlike the leaves of the oak. Another group, that of the Thalassianthidæ, is distinguished from the preceding by having all its tentacula short, pinnate, and branching, or papilliferous. One species only is known, _T. aster_, of a slate colour, which inhabits the Red Sea. [Illustration: Fig. 81. Phyllactus prætexta (Dana), natural size.] In the last group of Actiniadæ, as arranged by Milne Edwards, the polypes occur in clusters, and are multiplied by buds, rising from a common creeping, root-like, fleshy base; they thus present a sort of coriaceous polypier, as in _Zoanthus socialis_ (Fig. 82). In the British Channel this species, which Dr. Johnston has named _Z. Couchii_, after Mr. Couch, jun., is found along the Cornish coast, on flat slates and rocks, in deep water, and from one to ten leagues from the shore. It is very small, resembling, both in shape and size, a split pea. When living, its surface is plain but glandular, becoming corrugated when preserved. When semi-expanded, which is its favourite state, it elevates itself to twice its ordinary height, becoming contracted about the middle, like an hour-glass. When the creature is fully expanded, the tentacula become distended and elongated to about the length of the transverse diameter of the body; and they are generally darker at their extremities than towards the base. Like all the Actiniadæ, the present species possess a power of considerably altering their shape; sometimes the mouth is depressed, and at others it is elevated into an obtuse cone. "This is one of the most inactive of its order," says Mr. A. Couch; "for, whether in a state of contraction or expansion, it will remain so for many days without apparent change. In its expanded state a touch will make it contract, and it will commonly remain so for many days." The trailing connecting-band is flat, thin, narrow, glandular, and of the same texture as the polyp, sometimes enlarging into small papillary eminences, which, as they become enlarged, become developed into polyps.