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 geminus. The second 
appearance is in Chasmops limestone, which is the horizon in which 
it is found at Kinnekulle and in Vastergétland generally. 
At Kinnekulle, 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 Vastergétland 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 Vastergétland 
and Dalecarlia, Remopleurides sexlineatus, Ptychopyge glabrata, Ampyx 
rostratus, and Agnostus trinodus all occur in the zone of Dicrano- 
graptus clingant in Scania. The zone of Dicranograptus clingani is 
the one next above the zone of Nemagraptus gracilis, both in Scania 
and in Jemtland. 
In Gistrikland 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 
Gistrikland 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 lke 
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 platywrus, Ogygiocaris dila- 
tata, and Lituites lituus, fossils found in the Platyurus, Chiron, and 
Ancistoceras zones at Kinnekulle 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 a8, 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, 
