^C. eburnea.^ This species is found in tide-pools on algæ, especially on the red seaweeds, growing in bushy tufts from one half of an inch to an inch high. Calcareous, with horny joints; cells in two rows, semi-alternate, cylindrical, free at one end, bent; no operculum; ivory-white; ovicells large and pear-shaped. Common from Long Island Sound northward and on the Pacific coast. GENUS ^Tubulipora^ ^T. flabellaris.^ This species is found attached to slender branched algæ, in coral-like masses of long, crooked, tubular cells united at the base and spreading into fan-shapes placed flat against the fronds. It is sometimes one quarter of an inch in diameter. On the same alga may often be found /Crisia/, /Mollia/, and /Cellepora/. (Plate XLIX.) GENUS ^Diastopora^ ^D. patina.^ Tubular cells rise from a saucer-shaped disk about a quarter of an inch in diameter; cells lie obliquely or stand erect, and are crowded toward the center; margin of disk without cells; colony white and calcareous. Found on algæ and eel-grass from Long Island Sound northward. SUBORDER ~CHEILOSTOMATA~ In this suborder the zoœcia are either horny or calcareous, and the orifices are usually surrounded with spines and have opercula. The orifices generally have raised margins, or peristomes. Ovicells form helmet-like coverings overhanging the orifices. GENUS ^Ætea^ ^Æ. anguinea.^ Delicate, white, creeping, calcareous stems, from which rise numerous club-shaped cells, about one eighth of an inch high, each one with an aperture in the end. This species creeps in wavy lines along the fronds of algæ, and is frequently found on /Dasya/, /Griffithsia/, /Plocamium/, and eel-grass. [Illustration: PLATE XLIX. Tubulipora flabellaris. 1, Tubulipora flabellaris, natural size. Eucratea chelata. Cellularia ternata. 1, Cellularia ternata, natural size.] [Illustration: PLATE L. Caberea Ellisii. Bugula turrita. 1, Bugula Murrayana; 2, B. Murrayana, magnified; 3, B. Murrayana, a few cells, more highly magnified; 4, B. flabellata; 5, B. flabellata, magnified.] GENUS ^Eucratea^ ^E. chelata.^ A small, delicate species rising from a creeping stem. It has branches composed of single rows of horn-shaped cells having an oblique aperture on the side. Found at extreme low-water mark on hydroids, shells, stones, and /Fucus/. (Plate XLIX.) GENUS ^Cellularia^ ^C. ternata.^ Zoarium filamentous, spreading, about one inch high, white, calcareous, branched in a forking manner; cells long, narrowest at base, arranged in series of three and on the same plane, apertures oblique and facing one way; horny joint between each cluster of cells. This species grows in deep water from Cape Cod northward, and is found on objects washed upon the beach. (Plate XLIX.) GENUS ^Caberea^