RAYMOND: CORRELATION OF THE ORDOVICIAN STRATA. 245 



The next formation, Bi of Holtedahl's section, consists of practically 

 unfossiliferous shales and thin-bedded sandy limestone which passes 

 above into B2, sandy limestone and shale containing Coelosphaeridium 

 cyclocrinophihim. In the upper part of the same formation is a large 

 fauna which includes many species found in the Jewe of Esthonia. 

 Cyhele grewingki Schmidt, Chasmops marginata Schmidt, Porambonites 

 schmidti Noetling, Coelosphaeridium cyclocrinophilum Roemer and 

 Mastopora concaca Eichwald are among the striking species which 

 Holtedahl lists as common to the two regions. The thickness of this 

 formation is unknown but it must be over forty meters. 



Then follow two very fossiliferous zones both characterized by an 

 abundance of Cyclocrinites, and making a total thickness of about 

 twenty-three meters. These formations have a fauna entirely com- 

 parable to that in the Kegel of Esthonia. Holtedahl lists the follow- 

 ing species found in both B3 and the Kegel : — 



Bcmlicvs kcgelensis Schmidt, Chasviops maxima Schmidt, Chas- 

 mops bucculenta Sjogren, Fiery gometojms l-cgelensis Schmidt, Biicai- 

 nielJa lineata Koken, Leptaena aff. schmidti Tornquist, Platystrophia 

 biforata Schlotheim, Triplecia insularis Eichwald, Cydocrinites oclandi- 

 cus StoUey, C. vanhoeffeni StoUey, and C. balticus Stolley. 



Holtedahl correlated these latter zones, Bsa and Bsb, with the 

 Trinucleus shales of Sweden, the Trinucleus shales and Isotelus 

 limestone of Norway, and the Kegel and Wesenberg of Esthonia. 

 In regard to the correlation with the Trinucleus shales, Holtedahl 

 himself says that there are only two species, Illaenvs linnarssoni and 

 Remopleurides dorsospinifer common to the two. Neither of these 

 species is a guide fossil, Illaenvs linnarssoni in particular having a 

 very long geological range. It is worthy of note that none of the 

 Bohemian species which make so important a part of the fauna of 

 the Trinucleus zone of Sweden and the Christiania district is found 

 in B3 of the section in the Mjosen district, but the fauna is strictly of 

 the Russian type and belongs to another basin. In this case, the 

 difference can hardly be due to difference in facies, for the Trinucleus 

 beds of the Christiania district contain a large amount of limestone; 

 not a sandy limestone, it is true, but neither is the Kegel a sandy 

 limestone. Furthermore, we are not here dealing with graptolites 

 or other fossils highly sensitive to environmental conditions, but with 

 general faunas. 



In Jemtland, the Trinucleus shales appear to be absent, and among 

 the boulders of " Oestseekalk " are found many of the characteristic 

 fossils of the Kegel and Wesenberg limestones, indicating that these 



