1906.] ALCYONAKIANS FROM ZANZIBAR. 397 



only known to those having special acquaintance with these coasts, 

 I give here some notes on the various locaHties refei'red 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 Kiungani 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 my collecting was done on 

 Prison Island, which is one of these, while the naiue 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 bi-ight 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 neai-ly bai-e. 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 Zanzibar Town 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 Xeniidse 

 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 

 veiy barren. 



Ohuaka Bay 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 covei-ed with Halimeda sp., and the sides of the channels 

 with grass-like Zostera. A large baiak in the centi-e of the bay is 

 covered with large sponges, looking like stones at a little distance. 

 There is no coi-al anywhere in this area. Alcyonarians, chiefly 

 Xeniidse, 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). 



