4 GEOLOGICAL MEMOIES. 



of basins geographically separated, it is evident that in England 

 there is no distinct subdivision which can be considered as especially 

 the stage G of Bohemia ; and the same remark is applicable to stage 

 H, of which the fauna is but a feeble continuation of that of G. 



In Russia and the Baltic provinces the progress of discovery has 

 confirmed the equivalence, already laid down in 1845 by Sir E. 

 Murchison, between the Silurian rocks of the Isle of Oesel and those 

 of England ; but Dr. Schmidt remarks that the subdivisions of the 

 Ludlow rocks cannot be recognized in the upper zones of the Island 

 of Oesel, and it is important to observe that of the 43 species of fish 

 belonging to this zone, 12 of them, among which Pterichthys [Astero- 

 lejpis] occurs at Ohhesaare-Pank associated with Phacojos Down- 

 ingicB, Calymene Blumenhachi, Orthoceras huUatum, 0. trocheale, Car- 

 diola interrupta, Fterinea retroflexa, Petzia Salteri, StrojpJiomena 

 filosa, Chonetes lata, and other Wenlock and Ludlow fossils, showing 

 as remarked by M. Barrande, that the presence of fish-remains by no 

 means vitiates the Silurian character of the last phases of the third 

 fauna. Erom a comparison of the list of fossils supplied by Dr. 

 Schmidt with those of Bohemia, it appears that 21 species are com- 

 mon to both localities, of which 20 belong to stage E, and that, not- 

 withstanding the number of fish-remains, the highest zone of the 

 Isle of Oesel is anterior in age to stage G of Bohemia, but that fish 

 of many types appeared there at an earlier period than than they did 

 in the Silurian basin of Prague. 



In Sweden and Gothland stage E is represented by 22 and stage 

 E by 10 species common to those countries and Bohemia, thus con- 

 firming the views of Sir R. Murchison and Dr. Schmidt of the exist- 

 ence of the Wenlock and Ludlow rocks, the higher zones G and H 

 being entirely absent. In Norway, as in Sweden and Gothland, 

 nine-tenths of the species common to that locality and Bohemia 

 belong to stage E, stage E being but feebly represented ; beds referred 

 to the middle part of the Ludlow period being surmounted conformably 

 by unfossiliferous sandstones and marls 1000 feet in thickness, which 

 are considered by Prof. Boomer to be of Devonian age. In Thuringia, 

 Saxony, and Eranconia, beds corresponding with the first phase of 

 Barrande's third fauna, namely, zone E, are succeeded by deposits 

 placed more or less high in the Devonian series. The Silurian rocks 

 of the Harz have been referred by Prof. Giebel to the horizon of the 

 Wenlock in England and zones E and E in Bohemia, and the presence 

 of Monoprion Sagittarius removes all doubt as to their Silurian age ; 

 but the mixture of Lower Devonian forms with those of the third 

 fauna, together with several types of fishes, and especially Ctena- 

 canthus, recall the upper calcareous zones F and G of Bohemia ; but 

 the large number of species of Capulus which coexist with these fish- 

 remains in the Harz contrasts with the nearly total absence of that type 

 in zone G, whilst analogous forms are sufficiently common in zone E 

 and again in zone E ; and although some Brachiopods, like Rhyncho- 

 nella cuneata, are referable to the former, the greater number apper- 

 tain rather to the latter. At present, therefore, the data are too 

 fragmentary and incomplete for the position of these beds to be deter- 



