ON THE OCCFERENCE OF MARINE SHELLS. 351 



25. On the Occurrence of Marine Shells of Existing Species at 

 Different Heights above the Present Letel of the Sea. Bv 

 J. GwTN Jeeprets, Esq., LL.D., E.E.S., Treas. G.S. (E,ead 

 June 9, 1880.) 



"While engaged in working out for the Zoological Society tlie 

 Mollusca of the Expeditions which I undertook in 1869 and 1870 

 in H.M.S. ' Porcupine,' I was much struck by the discovery, at 

 great depths in the North Atlantic, of certain shells in a living state 

 which had been previously known only as Subapennine and South- 

 Italian fossils, and were considered extinct. 



To give some idea of the extent to which such changes of sea 

 and land must have taken place within a geologically recent period, 

 I subjoin an extract from my paper on some of the ' Porcupine ' 

 Mollusca, which was published in the ' Proceedings ' of the 

 Zoological Society for 1879, pages 586 and 587. With reference 

 to Malletia excisa, I said, " It will be seen that the last species, as 

 well as many other deep-water shells which have been noticed in 

 the present paper, are Calabrian and Sicilian Tertiary fossils. Be- 

 sides these species, others of the same kind, and which had been 

 also considered extinct (viz. Leda or Tindaria solida, Seg., Nucida 

 glabra, Ph., Oiii^ Malletia dilatata. Ph.), occurred in the ' ChaUeriger ' 

 Expedition. The communication between the North Atlantic and 

 the Mediterranean must have been formerly very different from 

 what it is now, when a barrier or ridge in comparatively shallow 

 water exists outside the Straits of Gibraltar, between Capes 

 Spartel and Trafalgar. It is improbable that deep-sea Mollusca, 

 even in their embryonic state, could have migrated or been trans- 

 ported under such conditions from one sea to another. The south 

 of Prance and Italy must have experienced a great elevation, 

 and perhaps a succession of them, since the Pliocene period. For 

 instance, the average depth at which Malletia excisa has been now 

 found living is 150 7-j fathoms, or 9044 feet, being very nearly five 

 sixths of the height of Mount Etna above the present level of the 

 sea ; and to this submarine elevation must be added the height of 

 the Pliocene beds above the sea-level. Professor Seguenza informs 

 me that M. excisa occurs in Sicily, as well as in Calabria, at a height 

 of 600 metres, or nearly 2000 feet, and that these fossiliferous beds 

 attain double that height in other parts of the same district ; so 

 that the total elevation may be estimated at from 11,000 to 12,000 

 feet. Mount Etna is 10,874 feet high." . 



Numerous fossiliferous beds, showing a greater or less amount 

 of oscillation, have been observed throughout the whole world, 

 and especially in the northern hemisphere. In Shetland and 

 Scotland they extend from a depth of 80 fathoms (480 feet) to a 

 height of at least 500 feet above the sea, making together an 

 elevation of nearly 1000 feet. In England and Wales they appear 



