I08 JOHAN KIÆR. M.-N. Kl. 



and there have been found remains of a Stremiclla which approximates to 

 Strenuella Linnarssoni if it is not identical with it. Equivalents to the 

 Holmia zone must therefore be sought further down in the profile. 



Now,, as fissure fillings of Lower Camarian sandstone are known from 

 Aaland, and as blocks of Lower Cambrian age with Lower Cambrian fossils 

 in considerable numbers are described by Wiman from the Northern Baltic 

 district, it is reasonable to suppose that the greater part of Sweden was 

 inundated by the sea during the Lower Cambrian transgression. The wester- 

 ly part of Varmland and the southern part of Dalarne^ must however be 

 taken to have been connected with the great continent which was found 

 in the southern part of Norway in the Lower Cambrian period. As the 

 northern frontier of this continent in Norway, we can take a line from 

 Tryssil Southwestwards to Gjøvik, from there almost due west past Valdres to 

 Gol. From there it is more uncertain, and possibly its further course took 

 a more northerly direction. 



Probable the Lower Cambrian transgression went from the south (Est- 

 land and Skåne) northwards to Northern Sweden and central and northern 

 Norway. In the oldest part of the Middle Cambrian period the south Nor- 

 wegian continent became inundated. Here, the transgression appears to 

 have gone from the north towards the south. 



We shall only discuss those of the Lower Cambrian districts outside 

 Scandinavia which have particular significance in establishing the position 

 of the Norwegian fauna in the Lower Cambrian succession. 



Here North America is of striking significance. The Lower Cambrian 

 strata and their fauna have of late years as is known, been minutely ex- 

 plored by Ch. D. Walcott^ who to a very great extent has widened our 

 knowledge of the oldest fossil formations. 



Walcott established in 1910 the following four zones in the Lower 

 Cambrian as a conclusion of his researches into the family Mesoiiacidae in 



North America: 



D. OleneUiis or upper zone. 



C. Callavia zone. 



B. Elliptocephala zone. 



.A. Nevadia or lower zone. 



The question now is, with which of these zones the Norwegian fossili- 

 ferous strata with their Holmia fauna are to be compared. That is not so 



^ In the Silurian District of Dalarne is the Silurian succession beginning with the Obolus 

 konglomerate (i. e. Dictyograpttis-zone). 



- Specially in "Cambrian Geology and Paleontology" (Smithson. Misc. Coll.) and "Cam- 

 brian Brachoipoda". 



