I916. No. 10. THE LOWER CAMBRIAN HOLMIA FAUJJA. lOI 



Cambrian. Torellella laevigata Lnrs. would thus have continued to 

 exist in the Middle Cambrian age. 



That this has really been the case is further supported by the circum- 

 stance that this form was not confined to a single zone in the upper part 

 of the Lower Cambrian. Thus in Sweden it was first described from the 

 Mickwitzia sandstone in Västergötland, which as we shall soon see, is older 

 than our Holiuia shales; as already mentioned, (Page 97) it is tound in 

 Norway in the oldest fossilbearing zone (the sandstone shales with trails) 

 it is common in our Holmia shales, and further it is found in the zone 

 containing Strcmiella Linnarssoni. The decisive factor, however, is that 

 after v. Schmalensee's discovery at Tomten, it is actually found with a fauna 

 of a Middle -Cambrian character (Page 99). 



We therefore consider it settled that the coarse clastic basal deposit 

 containing Torellella, which only occur rather far north, are of Middle 

 Cambrian age and must be parallellized with the Par. Ølandicus zone. It 

 is further possible that farther to the south it continued right to the Tessini 

 zone, this jbeing indicated by the complete lack of Torellella in the basal 

 deposits in the middle and southern part of the Christiania area (Slemme- 

 stad, Krekling, Skiensdalenj. The conditions mentioned at Slemmstad, 

 where limestone beds that are rich in remains of the Tessini fauna contain the 

 upper boulders of the conglomerate, also indicate this opinion. 



We may now proceed to give a short investigation of the downward 

 limits of our Lower Cambrian. 



As we have seen, the upper part of the Lower Cambrian in the nor- 

 thern part of the Mjosen region is formed by a somewhat massive grey- 

 green shale with some beds and lenticular bodies of sandy limestone. We 

 can here difl^'erentiate 3 faunistic zones (from above): 



1. The zone containing Strenuella Linnarssoni. 



2. » » — Holmia Kjerulfi. 



3. » » — Discinella Holsti. 



Then below these we have the Sandstone shales containing trails, 

 forming the lowest fossil-bearing zone. As shown by several profiles, this 

 apparently proceeds downwards with a regular transition to the thick banks 

 of huge quartz sandstone. We then reach the extremenly large, coarse 

 clastic series of beds that under the name of the Sparagmite formation 

 occupy a large area in the central part of Scandinavia. 



Of these series, it has been customar}- to reckon the Quartz sand- 

 stone, the thicknes of which at the northern part of Mjesen is estimated 

 at 500 meters, as Lower Cambrian, all the older series being comprised 

 under the term Sparagmite formation. The consideration of the age of the 



