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 MARINE ZOOLOGY 10. Membranipora monostachys. Busk. Colony incrusting, branching and reticu- lated. Zooecia ovate, slightly narrowed be- low ; aperture oval, occupying two-thirds of the front ; margins thin, bearing a central spine below, and sometimes a pair near the top; or armed with numerous (i8) delicate spines pointing inwards. Yarmouth, on mus- sel shells, etc., abundant (Harmer). The variety fossaria, forming friable sponge- like masses on the stems of plants, occurs near Yarmouth in ditches of brackish water a mile from the sea (Wigham). 11. Membranipora pilosa ijuinn.). Colonies in large flat incrusting sheets on Fucus and other weeds, between tide-marks. Aperture oval, surrounded by numerous mar- ginal spines {4-12), which bend inwards; a long horny spine usually present behind the area. Cromer (Harmer), Hasborough (P.), Yarmouth (Harmer). 12. Cribrilina annulata (Fabr.). Colonies forming small circular reddish crusts on Laminarla, shells or stones. Zocecia ovate, convex ; the sides wrinkled. About 6 pairs of perforated centripetal furrows. The raised calcareous bars between the furrows represent the marginal spines of Membranipora fused into a roof over the membranous aper- ture. Orifice suborbicular, with a thickened rim and 3 (or 4) terminal spines. Inside a mussel-shell off Yarmouth (P.). 13. Schizoporella linearis (Hassall). Colony incrusting, rose-coloured. Zooecia entirely calcareous, rhomboidal, in regular rows, separated by raised lines ; orifice round, with a pointed notch below, and 2-4 spines above. Avicularia minute, elevated, usually one on each side behind the orifice. On Sabellaria tubes, Yarmouth (Harmer). 14. Mucronella peachii (Johnst.). Colonies incrusting, calcareous, large, flat, of irregular outline ; on Laminaria, shells, stones, etc. Zocecia ovate, globose, notched around the margin (a relic of the gaps between ances- tral roofing spines, cf. Cribrilina). Orifice subquadrangular, mucronate, with 6 spines or denticles. No avicularia. Off Cromer and Hasborough (P.). 15. Lepra Ha pertusa (Esper). Colonies calcareous, circular, incrusting, orange-coloured, with a glistening lustre. Zocecia large, ovate, tumid, closely punctured ; orifice circular. Avicularia rare; small, oval, placed on one side near the orifice. On shells, stones, etc. Off Hasborough (P.). 16. Cellepora costaziiy Andouin. Colonies minute, calcareous, incrusting ; on stems of sertularian hydroids and algae. Zooecia crowded, ovato-cylindrical ; orifice terminal, with a prominent knob on each side bearing a minute avicularium. Off Has- borough (P.). II. CTENOSTOMATA 17. Alcyonidium gelatinosum, Linn. Colonies erect, gelatinous, smooth, lobed and branched, yellowish in colour. Height usually 3 to 18 inches. Off Yarmouth (P.). 18. Alcyonidium mytili, Daly ell. Colonies incrusting, fleshy, dingy white, the surface finely papillated and showing the hexagonal boundaries of the zooecia. Com- mon on shells, etc., Yarmouth (Harmer). 19. Vesicularia spinosa (Linn.). Colonies arborescent, horny, very delicate ; the main stems zigzagged, the branches dicho- tomously branched, bearing oval transparent zocecia at intervals. Height 4-12 inches. On stones, oyster-shells, etc. Off Yarmouth, common (Harmer). 20. Amathia lendigera (Linn.). Colonies arborescent, in tangled masses on fibrous algae and zoophytes. Zooecia cylin- drical, disposed in small groups immediately below the forks of the branches, each group consisting of 4-8 pairs arranged in two con- tiguous parallel rows. Tentacles 8. Yar- mouth (Harmer). 2 1 . Bowerbankia imbricata (Adams), var. dema. Colonies (in the variety) consisting of large cylindrical transparent zooecia, disposed in groups along a creeping stolon. Tentacles 10. On Fluitra, Yarmouth (Harmer). 22. Triticella flava, Dalyell. Zooecia laterally compressed, erect, ovate, attached to a creeping stolon by short stalks, on which they are movable. On backs of crabs {Portunus holsatus), Yarmouth (Harmer). III. CYCLOSTOMATA 23. Crista aculeata, Hassall. Colonies in small white tufts, the branches curling inwards. Zocecia tubular, calcareous, in double series, many bearing a long spine near the top ; the series are divided into seg- ments by yellowish horny joints. Height ^l inch. Yarmouth, on Flustra, Vesicularia and Hydroids (Harmer). 24. Diastopora patina (Lamarck). Colonies small (| inch diameter), white, calcareous, discoid ; surrounded by a broad. 85