430 HISTORY OF GEOLOGY AND PALEONTOLOGY. 



Coal deposits and the Carboniferous Limestone; the Grey- 

 wacke group included for the most part Werner's "Transitional 

 Series," but a Lower " fossiliferous group " of shales was differ- 

 entiated to comprise the oldest shales and greywackes in Wales 

 and Brittany. At the base of this fossiliferous formation, 

 De la Beche described the lower unfossiliferous series of strata 

 (schists, gneiss, granulite, etc.), and finally the unfossiliferous 

 eruptive varieties of rock. This text-book by De la Beche 

 had a wide circulation ; it was translated by H. von Dechen 

 (1835) into German, and by Brochant de Villiers (1833), in 

 somewhat altered form, into French. 



In the year 1833 the third volume of Lyell's Principles of 

 Geology^ appeared, the volume which was afterwards published 

 as an independent work, entitled The Elements of Geology. 

 This volume is especially memorable in stratigraphy for its 

 skilful solution of the difficult task of establishing a chrono- 

 logical sub-division of the Tertiary strata, that should apply 

 equally to the occurrences of this series in all the isolated 

 basins of deposition. With the help of P. Deshayes, Lyell 

 proposed the classification that has become permanent in the 

 science. 



Several years earlier, in 1829, Desnoyers, in an important 

 treatise, had proved that the different Tertiary basins had not 

 been filled with quite contemporaneous deposits, but that in 

 some of the basins deposition only commenced after others 

 had been partially or wholly silted up with sediments. The 

 Tertiary series could, he said, be naturally sub-divided into an 

 older and a younger group of sediments. 



In the following year, 1830, P. Deshayes 1 published the 

 results of his investigations on the resemblances and genetic 

 relations of the Tertiary Molluscs to the existing fauna. No 

 fewer than 2,902 species of Tertiary Conchylia, all derived 

 from known localities and horizons of deposit, were compared 

 with one another and with 4,639 living species. The results 



1 Paul Ger. Deshayes, born 1796 at Nancy, studied medicine in Stras- 

 burg and Paris, but never entered into professional practice. He taught 

 privately, and devoted his leisure to zoological and conchological studies. 

 From 1839 to 1842 he lived in Algeria, in order to make special researches 

 on the molluscan fauna of that neighbourhood. After his return, he held 

 private courses of lectures on geology and palaeontology, and in 1869 he 

 was appointed Professor of Conchology at the Museum in Paris; died on 

 the 24th May 1896. His splendid collection was acquired by the State, 

 and is exhibited in the School of Mines in Paris. 



