according to the prevailing dominants in a localised area. This present survey amply illustrates the replacement of C. columna by E. modestus in more brackish, silted up areas, and by C. brunnea with a change to oceanic conditions. All stages of gradation may be observed between these extremes. Where C. brunnea and C. columna occur together, the former occupies a belt above the latter (Stations 9, 15, 18–22, 28–30, 32–34). Within the wide vertical range of dominance of C. columna its place may be taken by any one of the co-dominants. According to each writer's preference these may be regarded as belonging either to the barnacle community or as dominants of a number of separate ecological groups. (b) New Zealand Widespread; Bay of Islands, Poor Knights, Piha, Tauranga, Wellington, Banks Peninsula, Otago. 11. Apophloea community. Apophloea Elminius Assn. (Cranwell & Moore, 1938, p. 386.) Carnahan, 1952, p. 37. Vertical Range: From M.H.W.N. to M.S.L. Occurrence: (a) Hauraki Gulf Forming dull red, leathery, circular patches on otherwise bare rock, occasionally giving rise to branched, finger-like projections. Notable on the basalt scoria at Rangitoto, though also common on firm, slab-like greywacke and on the smooth boulders of Little Barrier. Scarce or absent on Waitemata Sandstone. Where it occurs in sufficient density it can be termed the “red belt”. Apophloea is eliminated from community complexes subject to extreme wave exposure (Stations 2, 9, 11, 14, 15, 18, 20, 28, 30–31). (b) New Zealand Bay of Islands, Poor Knights (C. columna replaced by Elminius plicatus—Cranwell & Moore, loc. cit.) 12. Enteromorpha procera f. minuta community. Dellow, 1950, p. 365. Vertical Range: From M.H.W.M. to M.S.L. Occurrence: Hauraki Gulf Chiefly on sunny ledges of Waitemata sandstone, but also forming a bright green sward from autumn to spring on flat basalt rocks between Takapuna and Milford and elsewhere. Common above barnacles on wharf piles and embankments in sheltered harbours. On Little Barrier shores it is replaced ecologically by E. nana, though this species dominates mainly below M.S.L. on the boulders, and ascends above that level only on an iron boat ramp. Despite its interrupted horizontal distribution and the seasonal fluctuations in abundance, the Enteromorpha sward is an important feature of the upper midlittoral inside the Gulf; in fact it is quite reasonable to regard it as a distinct subzone of the barnacle zone, most conveniently termed the “green belt”. E. procera f. minuta may dominate wide stretches of flat or gently inclined rock on its own or it may codominate with Gelidium pusillum, Volsella neozelanicus and, in winter and spring, with brown trails of Scytosiphon or Pylaiella (Stations 3–5, 8, 20, 23–25, 28–30).