530 TEST ACE A ATLANTICA. 



alluding to this latter species, adds that ' although the shells 

 are now dead, they appear to be of more recent date ' than the 

 others ; and Mr. Benson referred to it in 1851 (vide ' Ann. of 

 Nat. Hist.' vii. 263) as absolutely ' recent,' — though as he gives 

 no evidence in support of his assertion, I think that in this he 

 was probably mistaken. The two largest, and most remarkable, 

 of these Bulimi (namely the B. auris-vulpina and the B. Dar- 

 winianus) belong somewhat to a type which has several expo- 

 nents in Brazil ; and this fact induced the late Professor E. 

 Forbes to hazard a theory on the quondam connection of St. 

 Helena with the east coast of South America. But it seems to 

 me that so sweeping an hypothesis requires stronger evidence 

 to support it than that which is supplied by the presence of a 

 couple of Grastropods which confessedly resemble their transat- 

 lantic congeners only to a certain extent ; whilst the circumstance 

 that much the same type of form exists equally in the Solomon 

 Islands and New Zealand makes its reception more difficult 

 still, — necessitating, as it would, the extension of the same land 

 of passage more than half-way round the circumference of the 

 globe ! Moreover there are the strongest reasons for believing 

 that the area of St. Helena was never very much larger than it 

 is at present, — the comparatively shallow sea-soundings within 

 about a mile and a half of the shore revealing an abruptly-de- 

 fined ledge beyond which no bottom is reached at a depth of 

 250 fathoms ; so that the original basaltic mass which was 

 gradually piled up by means of successive eruptions, from be- 

 neath the ocean, would appear to have its limit definitely 

 marked out by this suddenly-terminating submarine cliff, — the 

 space between it and the existing coast-line being reasonably 

 referred to that slow process of disintegration by which the 

 island has been reduced, through the eroding action of the ele- 

 ments, to its present dimensions. Therefore I cannot but think 

 that the conclusion of Professor Forbes was scarcely warranted 

 by the facts to which we have access ; though to a mind for 

 which mere speculation, as such, is attractive, it may carry with 

 it its own amount of weight, whatsoever that may be ; and, as a 

 still further aid to the acceptance of it, I may just add that 

 Professor Forbes likewise thought that the m^arine mollusks of 

 St. Helena (about which, nevertheless, almost nothing was then 

 known) ' dimly indicated ' ' a closer geographical relationship 

 between the African and American continents than what now 

 obtains ' [vide the ' Quarterly Journal of the Greological Society ' 

 viii. 198; 1852), — an ultimatuon at which I must candidly 

 confess that I have not been able to arrive. 



The genus Succinea constitutes a most conspicuous feature 

 in the Gastropodous fauna of St. Helena ; and this is all the 



