68 MR SMITH ON THE CHANGES 



I have endeavoured to institute as rigorous a comparison as 

 I could between the testacea of the two periods, and refer 

 to the catalogues which I have appended to this paper, for 

 the results. It will be observed that, although the greatest 

 proportion of the shells are identical with existing species, 

 there is a certain proportion which differs from them.* Of 

 those which are unknown, some may probably yet be disco- 

 vered in a recent state ; whilst others, in place of being spe- 

 cifically different from their recent congeners, may be only 

 varieties arising from the differentcircumstances under which 

 they were placed. Still, as the per-centage of unknown shells 

 is as great as that of the newer pliocene of the Sicilian de- 

 posits, it appears highly probable, that a considerable 

 change must have taken place in the fauna. 



The organic remains belonging to these deposits have 

 been termed Quaternery by some geologists, and Subfos- 

 sil by others. Professor Phillips includes the beds in 

 which they are found amongst the post-tertiary and modern 

 deposits, — although with some doubt ; observing, that it is 

 difficult to ' c discriminate between the Sicilian tertiaries 

 with 95 per cent, of existing species of shells and the con- 

 chiferous gravels and sands of Holderness and Lancashire, 

 in which, among twenty species of shells now living in the 

 German Ocean, one occurs which is not yet known. If the 

 Lancashire shells are, like those of Specton, Udevalla, and 

 the coasts of Devon and Calvados, raised beaches, and to 

 be classed in the modern epoch, why are the Sicilian ranked 



* At the late meeting of the British Association at Newcastle, I had 

 an opportunity of clearing up some points of interest respecting the 

 unknown species of shells belonging to these deposits, and have to ac- 

 knowledge the advantage I derived from the kind assistance of Messrs 

 Adamson and Alder, and from my visits to the Museum of Natural 

 History, which is arranged in a manner well worthy of the scientific 

 eputation of that splendid city. 



