FAUNA OF ST. CROIX ISI^AND 09 



There is good reasou for suspecting that at no very 

 distant period, geologically speaking, the island was com- 

 pletely submerged. In the neighbourhood of Kedhouse 

 near Port Elizabeth, and at various localities in the 

 Alexandria district, there may be found deposits of 

 marine shells in fossilised condition at high elevations. 

 These shells must have been laid down under marine or 

 estuarine conditions, in which case the land surfaces in 

 this })art of S. Africa have been raised at least a thousand 

 feet since mio-pliocene times. Even within the period of 

 penguin occupation, great changes of this nature can be 

 traced: in his account of penguins on the Guano islands 

 oil' the West Coast of Cape Colony, Mr. Hammond Tooke 

 remarks : — There are now isolated mounds of guano on 

 rocks cm the mainland, shewing how the sea has receded 

 from the land in comparatively recent times, guano being 

 deposited only on islands. There is possibly direct 

 evidence of former submarine conditions on St. Croix 

 island, for certain calcareous incrustations found be- 

 tween the hard quartzite rocks at various elevations 

 greatly resemble material formed under the sea by red 

 algae and other mai-ine organisms. 



Under these circumstances, an island so recently formed 

 is not likely to have any relics of the ancient terrestrial 

 fauna or flora of Africa. For the most part, its 

 population is a mere fragment of the mainland fauna, 

 brought probably by casual agencies such as floating 

 logs, or in some cases by winds. Actually, it is ver\ 

 small in number of species but rich in individuals. 



The flora of St. Ci-oix is completely devoid of trees or 

 bushes, and I saw neither grasses nor sedges. The only 

 plant that thrives abundantly is a white-flowered 

 Mcsembryanthemum — M. angnlatiim, according to Dr. 

 Schonland who tells me that the species occurs also on 

 Bird Island as well as on the mainland. It growls 

 amongst the rocks throughout the island. There is no 

 soil as ordinarily understood : between the rocks is a 

 little sand more or less mixed with guano. 



