46 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 6, 



constancy of character from the Isle of Odinsholm and the cliffs of 

 Baltisch Port to Narva and the hills south of St. Petersburg, where 

 it is part of the Lower Silurian of M. Kutorga*. The most im- 

 portant fossils of this rock are its Orthoceratites, Orthoceras duplex, 

 O. vaginatum, 0. undulatum, Schlotheim and Quenstedt, and the 

 O. acutum, Eichw. These are accompanied by Asaphus expansus, 

 A. raniceps, Illcenus crassicauda, Lichas Hubneri, L. verrucosus, 

 Cheirurus exsul, Beyr., Lituites convolvans, L.falcatus, L. Odini, 

 Eichw., Bellerophon locator, Eichw., B. megalostoma, Eichw., 

 Porambonites cequirostris, Rhynchonella nucula, Orthis calligramma, 

 O. injlexa, 0. extensa, O. obtusa, Orthisina adscendens, Siphono- 

 treta unguiculata, S. verrucosa, Sphceronites aurantium, Echino- 

 sphcerites Balticus, Hemicosmites pyriformis, Receptaculites orbis, 

 Eichw., &c. 



Towards the upper limit of this stage, and in the eastern part 

 of Esthonia, there is found a bituminous shale, known as " brand- 

 schiefer" or inflammable schist, formerly described by Colonel Hel- 

 mersenf . Occurring at Tolks and Pungern, it is very rich in well- 

 preserved fossils, which seem to connect the underlying calcareous 

 stage with the next overlying limestone, many of the species being 

 peculiar to the deposits. Trilobites abound, but have not yet been all 

 identified, though among them are Asaphus acuminatus, Boeck, 

 Cheirurus aculeatus, Eichw., Ampyx, Trinucleus, and Phacops, 

 with Beyrichia and Leperditia, Leptcena sericea, L. Humboldtii, and 

 other fossils. 



The second limestone is a fine-grained, yellowish, and bluish 

 rock, occasionally having almost the aspect of lithographic stone, 

 and passing often into marly beds particularly rich in fossils. 

 This stage forms the northern half of the Isle of Dagden, and thence 

 passes eastwards in a broad zone across Esthonia to the south of 

 Narva and into the Government of St. Petersburg, where it has been 

 called Upper Silurian by M. Kutorga. 



In reality, however, says M. Schmidt, this limestone is only the 

 superior member of the unquestionable Lower Silurian rocks of 

 Russia. 



xlmong its prevailing fossils may be cited Lichas angusta, Beyr., 

 L. Dalecarlica, Ang., Calymene brevicapitata, Portl., Encrinurus 

 multisegmentatus, Portl., Phacops, several species of Lituites anti- 

 quissimus, Eichw., Murchisonia bilineata, Hall, Subulites elongatus, 

 Conr., Strophomena Asmusii, S. rugosa (distinct from S. depressd), 

 Leptcena deltoidea, L. sericea (very abundant), Orthis Actonice, 

 O. testudinaria, Orthisina anomala, 0. Verneuilii, Streptoplasma 

 corniculum, Heliolites megastoma, H. favosa, Ptilodictya acuta, P. 

 pulchella, Hall, Coccinium proevum, Eichw., Cyclocrinites Spaskii, 

 Eichw., and Calamopora patellaria, Kutorga J. 



The two preceding stages contain the following fossils in com- 



* See the Map of the Government of St. Petersburg, by M. Kutorga. 

 f Annuaire du Journal des Mines de Russie, 1838, p. 97. 

 X The so-called Pentamerus ventricosus, Kutorga, of this stage seems to be a 

 Porambonites of Pander. 



