38 Mr Grossland, The Coral Reefs of Pemba Island 



rock. For instance, Mesale,Kokota, and Fundu Islets are all of coral 

 rock, while Funzi and the long promontories of the main island are 

 of sand with a limestone foundation. This difference of material is 

 rendered conspicuous not only by the differing shapes of the 

 islands, but by the characters of the vegetations they support, the 

 outer flat coral islets, e.g. Kokota, being clothed with dense bush, 

 the higher rounded sandy islets, e.g. Funzi, having open spaces of 

 grass and usually wild palm trees 1 . As one proceeds up Chaki 

 Chaki Bay the level of the coral rock gets lower and lower, dis- 

 appearing below low tide level just beyond Banani. 



Pemba and Zanzibar are thus somewhat similar and similarly 

 situated figures, with this difference, that the channel between 

 Pemba and the mainland averages a depth of 400 fathoms and is 

 entirely free from shoals, other than the mainland barrier referred 

 to below. The hundred-fathom line closely encloses the island at a 

 distance of from two-thirds to one mile on all sides except the 

 north, where its distance from the land is from seven to eleven 

 and a half miles, or from the outlying reefs from three to seven 

 and a half. 



Pemba therefore is an independent formation, in contrast to 

 Zanzibar, which is an enlarged portion of the barrier reef of the 

 mainland coast. 



The Reef of the East Coast. 



The east coast differs from that of Zanzibar in the rarity of 

 sand beaches, the lines of cliff being almost continuous. 

 The reef differs in 



(1) its narrowness, its breadth varying from one-sixth or 

 less up to two-thirds of a mile, as against one or two miles in the 

 case of Zanzibar ; 



(2) there is no boat channel ; 



(3) the reef edge is covered with organisms of genera 

 absent from the corresponding position in Zanzibar. 



The characters of the surface rock of the reef, and the gravel 

 and coarse sand matted together by the roots of Zostera, the slope 

 of the outer edge, and so on, are exactly as seen in Zanzibar. 

 The boat channel, however, is rudimentary, being represented by 

 numerous pools a foot or two deep. The straight outline of the 

 edge and the uninterrupted surface of the outer slope are alone 

 sufficient proof that the reef did not originate through the growth 

 of organisms in situ. The stunted corals, Alcyonaria (including 

 Tubipora) and abundant foliaceous and encrusting nullipores, and 



1 A similar difference is noted by Gardiner as rendering conspicuous the 

 distinction between the limestone and volcanic islands of the Fiji Group. On 

 Funafuti, Eotuma, and Fiji, Proc. Camb. Phil. Soc. Vol. ix, Pt viii. 



