338 Geological Society. 



certain that the fossils contained in the transition rocks of the islands 

 and shores of the fiord of Christiania agree most nearly with those 

 in the lower part of the English Silurian system ; and, Mr. Lyell 

 adds, that in mineral character the Norwegian rocks also resemble 

 more closely that part of the system as exhibited in Shropshire and 

 Radnorshire than the upper. 



The two principal divisions of the Christiania group consist, first, 

 of dark shale, slate and clay, some of the beds being highly calcareous, 

 and enclosing Graptolites, Trilobites and other fossils ; also of beds 

 of grit ; and secondly, of strata of smoke-grey limestone abound- 

 ing in corals, and of sandstone, shale and conglomerate. Prof. Keil- 

 hau, who has long studied these formations, of which the beds are 

 much disturbed, inclines to the opinion that the second di^^sion is 

 the uppermost deposit. Among the fossils common to the Chris- 

 tiania series and the English lower Silurian strata are Calymene punc- 

 tata, Trinucleiis Caractaci, Orthoceras conicum, Bellerophon bilobatus, 

 Pentaments ohlongus and Graptolites Murchisonhis : other species of 

 Trilobites, which are not British, partake of the same type as those 

 which characterize the Caradoc sandstone or LlandeUo flags. 



In the island of Langoen in the fiord of Christiania, a few miles 

 from Holmstrand, Mr. Lyell examined a limestone rich in fossils. 

 It dips regularly towards the west, or in the direction of Holm- 

 strand ; and he believes that it constitutes, together with the quartz- 

 ose sandstone near that town, one of the uppermost divisions of the 

 Christiania formation. Among the corals which he obtained from 

 the limestone, the following have been determined as identical 

 with British species ; and as five of them have been found in En- 

 gland, hitherto, only in the upper Silurian strata, and others both in 

 the upper and lower, Mr. Lyell is of opinion that the Langoen deposit 

 may indicate a passage from the lower to the upper Silurian rocks. 



Stratigraphical position in the English 



Genus and Species. Silurian System. 



Catenipora escharoides .... Aymestry limestone to Llandeilo flags. 



Ptilodictya lanceolata Wenlock limestone. 



Stromatopora concentrica . . Wenlock limestone and shale. 

 Favosites Gothlandica .... Aymestry limestone to Caradoc limest. 



fibrosa Ditto, , ditto. 



polymorpha .-' . . Upper Ludlow and Aymestry limestone. 



Limaria fructuosa Wenlock limestone and shale. 



Millepora ? repens Wenlock limestone. 



The same beds also contain Euomphalus subsulcatus, Producta 

 eiiglypha, and Cytherina Baltica. 



A series of fossils lately obtained at Christiania by Mr. Bunbury. 

 lead to precisely similar results*. The total number of species con- 

 tained in Mr. Lyell and Mr. Bunbury's collections amounts to sixty, 



* Mr. Bunbury has informed Mr. Lyell that Asaplius expansus, Illcenus 

 crassicauda and a SphcEronites, common in the Silm-ian strata of Christiania, 

 arc also characteristic, according to M. de Verneuil, of Silurian beds near 

 St. Petersburg. These species are apparently unknown in England, but 

 Mr. Lyell suggests that the Russian strata containing them will probably 

 prove to be lower Silurian. 



