/( )OLOGY. MOLLUSCA. 193 



in malaco-geography than the close affinity existing between 

 the European Tertiary land Mollusca and those now inhabiting 

 the West Indies. 1 To explain this relationship existing be- 

 tween two regions separated by the whole expanse of the 

 Atlantic various theories have been offered. One of the most 

 plausible is that which bridges the Atlantic by an ancient 

 (Eocene, early and Middle Miocene) continent an Atlantis, 

 This view has been advocated by the well-known concholo- 

 gist Dr. W. Kobelt 2 and' by others. 



But although this theory explains many anomalies in the 

 distribution of mollusks, I must freely confess that the objec- 

 tions to it seem to me almost insurmountable. The recent 

 work of the Challenger, Blake, and other deep-sea explora- 

 tions, all tend to confirm the view held by Guyot, Dana, 

 Agassiz and others, that the great oceanic basins, practically 

 as they exist to-day, are of great antiquity, and render the 

 existence of a former Atlantic continent with any considerable 

 Western extension, highly improbable. 



A view more in accordance with the facts with which we 

 are at present acquainted seems to me to be the following: It 

 is a well ascertained truth that until towards the close of the 

 Miocene, large portions of Northern Africa as well as Europe 

 were submerged ; and it appears probable that the westward 

 flowing equatorial current of the Indian Ocean extended across 

 northern Africa, and united with the Atlantic northern equa- 

 torial current, which now flows westward from northern 

 Africa through the Antilles into the Gulf of Mexico. This 

 current would afford a means of transport not only for the 

 free swimming embryos of marine mollusks (and there are not 



1 This affinity, although doubtless very great, has been considerably exaggerated. 

 There is, for instance, no warrant for referring European Tertiary species to the ex- 

 clusively New World genera Pleurocera, Anculosa, Tulotoma, Mesodon, Carinifcx, 

 Afelantho, and others. There seems to have been no infusion of European Tertiary 

 types into the North American snail fauna east of the Californian region. This fauna 

 is truly autochthonous. 



2 Nachrichtsblatt d. deutschen Malak. GeselL, 1887, p. 147 



