35 
UPPER SILURIAN ROCKS OF OESEL, ETC. 
Zuboff family, and doubtless forms part of the calcareous zone observed by M. 
Dubois de Montpereux at Pocroi 1 . This limestone is thin-bedded, of grey colour, 
in parts compact, in parts earthy, here and there graduating into a spotted red and 
green rock, with soft shale partings. The exceptional beds are yellowish, having 
slightly a magnesian aspect, and the surfaces are frequently marked with fucoid- 
like bodies. We detected about fifteen species of fossils in our hurried view of this 
deposit (including those from Meshkovitza, north of Shavli), and among these are 
Pentamerus borealis (Eichw.), Terebratula Duboisi (nob.), Favosites Gothlandicus, 
Calenipora escharoides, Monticularia Sternbergii (Lons.), Stromatopora concentrica, 
Cyalhophyllum ceratites (Goldf.), and fragments of Euomphali and indeterminable 
Encrini. 
On the whole, it would appear (though the western end of the tract has not been 
examined by us) that in no part of the mainland of the Baltic provinces is there 
any Silurian stratum of younger age than the equivalent of that peculiar lime- 
stone with Pentameri which has been hitherto classed as the uppermost bed of the 
Lower Silurian rocks. In Russia, however, as in Scandinavia, the fossils of this 
calcareous zone are, as indeed we should expect they must be, of an intermediary 
character, and already contain some true Upper Silurian forms. Such, indeed, 
ought to be the case ; for this limestone is nothing more than the bed of passage 
between the two groups (see tabular view to the right of the Map). 
Upper Silurian Deposits. — If nowhere apparent on the mainland, true Upper 
Silurian strata are clearly developed in the Isles of Oesel and Dago 2 . Even the 
corals 3 collected from tlience by M. Eichwald and submitted by him to our inspec- 
tion left no doubt in our minds on this subject when we first saw them. M. Pan- 
der has, indeed, completely confirmed the view by communicating to us the results 
of his examination of the Isle of Oesel. In the limestone which forms the funda- 
mental rock, he cites the undermentioned fossils : — 
Calenipora escharoides, C. labyrinthica, Favosites Gothlandica, F. hasaltica, F. polymorpha, Syringopora reticulata, 
Aulopora serpens; A. conglomerata, Millepora repens, Porites pyriformis, Cyathophyllum turbimtum, &c., Orthoceratites 
1 See Karsten Archiv. 1830, and Leonhard Jahrbuch 1832. The latter contains a description of the 
fossils hy M. v. Buch (p. 109). 
- From what M. Eichwald says of the presence of the Illoenus crassicauda, Spiri/er lynx and Orthis 
tricjonula in the Isle of Dago, it would seem that portions of both the lower and upper groups may there 
co-exist. (Urwelt des Russlands, H. 2.) 
3 These corals have been compared and identified with typical Silurian forms by our valued friend 
Mr. Lonsdale, who has so well described the Silurian and Devonian corals of England. (See Sil. Syst. 
p. 675, plates 16 et seq., and Trans. Geol. Soc., plate 58, and descriptions and figures in the Appendix (A.) 
to this volume.) The best species of corals we possess are these supplied by M. Eichwald. 
