Geographical Distribution. 231 



of the isolated species, and the degree in which theii 

 nearest allies on the mainland are there confined 

 to narrow ranges, and therefore less likely to keep 

 up any biological communication with the islands. 



St. Helena. A small volcanic island, ten miles long 

 by eight wide, situated in mid-ocean, noo miles from 

 Africa, and 1800 from South America. It is very 

 mountainous and rugged, bounded for the most part 

 by precipices, rising from ocean depths of 17,000 feet, 

 to a height above the sea-level of nearly 3,000. 

 When first discovered it was richly clothed with 

 forests ; but these were all destroyed by human 

 agency during the i6th, i7th and i8th centuries. 

 The records of civilization present no more lament- 

 able instance of this kind of destruction. From a 

 merely pecuniary point of view the abolition of 

 these primeval forests has proved an irreparable 

 loss ; but from a scientific point of view the loss 

 is incalculable. These forests served to harbour 

 countless forms of life, which extended at least from 

 the Miocene age, and which, having found there an 

 ocean refuge, survived as the last remnants of a remote 

 geological epoch. In those days, as Mr. Wallace 

 observes, St. Helena must have formed a kind of 

 natural museum or vivarium of archaic species of all 

 classes, the interest of which we can now only surmise 

 from the few remnants of those remnants, which are 

 still left among the more inaccessible portions of the 

 mountain peaks and crater edges. These remnants 

 of remnants are as follows. 



There is a total absence of all indigenous mam- 

 mals, reptiles, fresh-water fish, and true land-birds. 

 There is, however, a species of plover, allied to one 



