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Show 1906.] ALCYONARIANS FROM ZANZIBAR. 397 only known to those having special acquaintance with these coasts, I give here some notes on the various localities referred to in this report*. It must be borne in mind that the Island of ZANZIBAR has a length of 60 miles, and is 20 miles wide at the latitude of the town. It is unfortunate that as the same name refers to both island and town, the locality ' Zanzibar' would include every kind of habitat, while ' Beach near Zanzibar Town' refers to only one, or to two, including the special point towards K I U N G A N I which is referred to later. Zanzibar Harbour is really an open roadstead, partially protected by scattered islets to the north and west and by reefs to the south-west. A considerable amount of m y collecting was done on Prison Island, which is one of these, while the name of another, Baui (or Bawe), occurs frequently in the reports of Stuhlmann's collections. At low spring-tide the shores of Prison Island are over large areas literally blight blue with Xenias of that colour, and this is the case in very many parts of these coasts. Above the level of low spring-tides very little of anything occurs, the rock-flats being nearly bare. This applies to every part of these coasts, but some specimens, referred to in the report, were collected higher up the shore. The shore at Z A N Z I B A R T O W N is, at low-tide level, muddy, and Alcyonaria are nearly absent, except at one point towards KIUNGANI, where a copious salt-spring issues from under the slabs of conglomerate which form the upper part of the shore. Here an oasis of wonderful richness occurs in the desert of mud, and corals and alcyonaria cover the whole shore. Brown Xeniidaa and several fleshy Alcyoniidse are found here in great abundance, some colonies of the latter attaining to the size of a yard across. Dredging just below this level gives good results, but at depths over 3 fathoms or so most of the eastern part of Zanzibar Channel is very barren. C H U A K A B A Y is a large indentation on the East Coast of Zanzibar Island, physically conspicuous, and so coming to be marked on good atlases, but of no commercial utility, producing only a little mangrove timber. At low spring-tides it presents a great expanse of mud, with channels of water one or two fathoms deep. The lower parts are thickly covered with Halimeda sp., and the sides of the channels with grass-like Zostera. A large bank in the centre of the bay is covered with large sponges, looking like stones at a little distance. There is no coral anywhere in this area. Alcyonarians, chiefly Xeniidae, abound among and upon these weeds, encrusting forms on the bases of the Zostera. £"* For more detailed information, see Proc. Camb. Phil. Soc. xi. p. 493 & xii. p. 35 (1902). |