304 ISLAND LIFE 



sufficient care to make it worth while to refer to them in 

 detail ; but the land-shells have been carefully collected 

 and minutely described by Mr. Wollaston himself, and it is 

 interesting to see how far they agree with the insects in 

 their peculiarities and affinities. 



Land-shells of St. Helena. — The total number of species 

 is only twenty-nine, of which seven are common in Europe 

 or the other Atlantic islands, and are no doubt recent 

 introductions. Two others, though described as distinct, 

 are so closely allied to European forms, that Mr. Wollaston 

 thinks they have probably been introduced and have 

 become slightly modified by new conditions of life ; so that 

 there remain exactly twenty species which may be con- 

 sidered truly indigenous. No less than thirteen of these, 

 however, appear to be extinct, being now only found on 

 the surface of the ground or in the surface soil in places 

 where the native forests have been destroyed and the land 

 not cultivated. These twenty 23eculiar species belong to 

 the following genera: Hyalina (3 sp.), Patula (4 sp.), 

 Bulimus (7 sp.), Subulina (3 sp.), Succinea (3 sp.) ; of 

 which, one species of Hyalina, three of Patula, all the 

 Bulimi, and two of Subulina are extinct. The three 

 Hyalinas are allied to European sj)ecies, but all the rest 

 appear to be highly peculiar, and to have no near allies 

 with the species of any other country. Two of the Bulimi 

 (B. cncris ruljnna: a.iid B. claricinianus) are said to some- 

 what resemble Brazilian, New Zealand, and Solomon 

 Island forms, wliile neither Bulimus nor Succinea occur 

 at all in the Madeira group. 



Omitting the species that have j^robably been introduced 

 by human agency, we have here indications of a somewhat 

 recent immigration of European types which may perhaps 

 be referred to the glacial period ; and a much more ancient 

 immigration from unknown lands, which must certainly 

 date back to Miocene, if not to Eocene, times. 



Absence of Fresh-water Organisms. — A singular pheno- 

 menon is the total absence of indigenous aquatic forms of 

 life in St. Helena. Not a single water-beetle or fresh- 

 water shell has been discovered ; neither do there seem to 

 be any water-j)lants in the streams, except the common 



