RAYMOND: CORRELATION OF THE ORDOVICIAN STRATA. 233 



with the Lower Dicellograptus shale of Sweden can be made. Echino- 

 sphaerites has not yet been reported directly associated with a grap- 

 tolite fauna containing diagnostic species. The shales with the Lower 

 Dicellograptus faunas are found at the north in Jemtland and at the 

 south in Scania, in both of which places Echinosphaerites is absent. 



On Oeland, Echinosphaerites occurs at two horizons. The first 

 occurrence is in the Platyurus limestone, in strata below the Chiron 

 limestone, which contains Didymograptus gcminus. The second 

 appearance is in Chasmops limestone, which is the horizon in which 

 it is found at KinnekuUe and in Vastergotland generally. 



At KinnekuUe, Echinosphaerites is found in the Chasmops lime- 

 stone, which is a formation consisting of limestone interstratified with 

 shale, the shale holding undetermined graptolites. Very little seems 

 to be known of the detailed distribution of the faunas in the Chasmops 

 formation in Vastergotland but the general consensus of opinion seems 

 to be that the Echinosphaerites is confined to the lower portion. Of 

 the trilobites listed from the Chasmops limestone in Vastergotland 

 and Dalecarlia, Remopleuridcs sexlincatus, Ptychopi/gc glahrata, Ampyx 

 rostratus, and Agnostus trinodus all occur in the zone of Dicrano- 

 graptus cUngani in Scania. The zone of Dicranograptus dingani is 

 the one next above the zone of Nemagraptus gracilis, both in Scania 

 and in Jemtland. 



In Gastrikland and Dalecarlia conditions seem to be somewhat 

 similar to those in Russia, for in Delarne the Platyurus limestone 

 contains a layer practically made up of "linsen," and boulders from 

 Gastrikland referred to the Chiron limestone contain "linsen" and 

 such typical Russian species as Asaphus kowalewski, A. cornutus, and 

 Christiania oblonga. In other boulders, said to be lithologically like 

 the Chiron limestone, but referred by Wiman to the Chasmops lime- 

 stone, Echinosphaerites aurantium, and Christiania oblonga are found. 



In the Christiania district of Norway, as has already been stated, 

 the Gigas limestone is succeeded by black shale and limestone, forty 

 to forty-five meters thick, with Didymograptus geminus. Other 

 significant fossils found here are Asaphus platyurus, Ogygiocaris dila- 

 tata, and Lituites lituus, fossils found in the Platyurus, Chiron, and 

 Ancistoceras zones at KinnekuUe and on Oeland, leaving no doubt as 

 to the correlation of these strata. Following this zone which is known 

 as 4 aa, is the zone 4 a/3, the zone of Echinosphaerites aurantium . Here 

 the 'strata are dark blue to black limestone and dark shale inter- 

 stratified and the thickness is about fifty meters. The Echinosphae- 

 rites are confined to certain layers and various trilobites are present. 



