Introduction. 



T. 



he youngest Silurian limestones and shales with marine fauna in 

 the Kristiania area are superimposed by a huge series that in the main 

 is composed of sandstone. This sa)iflstone serirs. which forms the 

 completion of our palæozoic sediments, and which was designated stage 9 

 by Kjerulf (stage 10, Brøgger) has been studied but slightly from a 

 stratigraphical point of view, and it has been impossible so far to determine 

 the age, owing to lack of fossils. As it superimposes conformably very 

 young Upper Silurian limestone of the Ludlow series, and its sediments 

 remind one of the faciès development of the Old Red sandstone, Mur- 

 chison as early as the year 1844, assumed that it was Devonian. This 

 theorv has been accepted by most Norwegian geologists since that time, 

 and I came to the same conclusion during my investigations of the 

 Upper Silurian in the Kristiania area (1908). 



In the following paper I shall give the first account of my discovery 

 of undoubted fossils in this series. In the lower part I found a remark- 

 able new fauna, which is not only of considerable palæontological interest, 

 but which has also great stratigraphical significance. It shows that our 

 previous views respecting the age of the sandstone series have been 

 erroneous. 



In the autumn of 1909 I commenced to study the lower part of the 

 sandstone at Ringerike, which was to some extent known to me from 

 my earlier investigations. I was fortunate enough immediatel)- to make 

 a discovery that far exceeded my expectations. 



In the section of the lower part of the sandstone series at Rudstangen 

 on the west side of Kroksund, we discovered the first remains of fish in 

 the solid rock. Although this first fragment of fish was almost the only 

 one that could be seen on the surface of the rock, it was found on closer 

 examination that these layers contained the remains of unique fishes and 

 crustaceans in ([uite considerable quantities. Moreover one quite new fauna 



