Mr Smith on the Changes of the Level of the Sea. 393 



ones in Sweden. I have often met with beds of shells imbed- 

 ded in marly clay, which had received a violet colour from the 

 decomposition of the common mussel {Mytilns edulu), exactly 

 as described by him.* 



The question as to the identity of the flora and fauna of the 

 present period, with that of submergence, is an important one. 

 It would perhaps be premature to say with certainty, whether 

 they are identical or not. With regard to the vegetation no 

 observations which have yet been made shew any difference be- 

 tween it and the existing race of plants. But too little has 

 been done in this department to be of any value in settling the 

 question. The same observation applies to the remains of birds 

 and land animals ; or to those of cetaceae, Crustacea, algae, zoo- 

 phytes, and other marine remains which have been found in 

 these deposits. 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 pa- 

 per for the results. It will be observed that, although the 

 greatest proportion of the shells are identical with existing spe- 

 cies, there is a certain proportion which differs from them.-f* 

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

 vered in a recent state ; while others, in place of being specially 

 different from their recent congeners, may be only varieties 

 arising from the different circumstances under which they were 

 placed. Still, as the per-centage of unknown shells is greater 

 than that of the newer pliocene of the Val di Noto in Sicily, it 

 appears highly probable, therefore, that some change in the 

 fauna must have taken place. 



The organic remains belonging to these deposits have been 

 termed Quaternery by M. Risso^ and subfossil by other geolo- 

 gists. Professor Phillips includes the beds in Avhich they are 

 found amongst the post-tertiary and modern deposits, — although 

 with some doubt ; observing, that it is difficult to *' discriminate 



• Phil. Trans. 1835, p. 1. 



t At the late meeting of the British Association at Newca.stle, I had au 

 opportunity of clearing np some points of interest respecting the unknown 

 species of shells belonging to these deposits, and have to acknowledge 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 ar- 

 ranged in a manner well worthy of the scientific reputation of that splendid 

 city. 



