191 I. No. 7- A NEW DOWNTÜNIAN FAUNA OF THE KRISTIANIA AREA. 9 



to pass evenl\- over the fossiliferous Upper Silurian limestones and shales. 

 The section is broken by Kroksund with its small islands. The complete 

 series cannot therefore be seen at this spot, and the determination 01 

 its magnitude is also rendered difficult by the faults which undoubtedh- 

 cut through the Sound, although their dimensions cannot yet be deter- 

 mined with exactitude. I believe however, all the most important 

 members of this series can be established. In the greater part of the 

 lower series we find banks and layers of hard, compact, calcareous 

 sandstone, with flakes of mica and shaly flakes, alternating with irregular 

 thinly laminated schistose sandstone; we also find deposits of purer 

 shale. The colour of these sediments is generallv a deep reddish brown, 

 more rarely a grayish brown or green. The compact sandstones ha\e 

 more frequently a paler tint. 



In this vast series, thick compact beds of calcareous sandstone 

 occur at se\eral levels and in considef-able bulk. 



The lowest of these is seen exposed in sections on the north-west 

 side of Kroksund. on the little island in Kroksund itself, and on UK- 

 Island and the neighbouring small islands in Stensfjord. At these spots 

 we invariably find between the thick beds of sandstone of an ordinär)- 

 t\-pe, irregular beds of a redbrown, characteristic sandstone that is more 

 calcareous, often with a fine diagonal bedding. It is possibK- in these 

 beds, that the small fragmentary fish remains discovered by BjØRLYKKE 

 in a boulder near Aas High School of Agriculture, had their origin. 



These beds are so characteristic that they could probabh' be employed 

 for a minute classification of the lower part of the sandstone. I will 

 not however for the present fix any definite zones, since further study 

 would possibly lead to alterations. 



The development of the series appears to have been somewhat 

 uniform above and below the said horizon; I may however mention as 

 one peculiarit\- of the upper beds, that the brown-red sandstone is often 

 full of small concretions — both round and irregular — composed of 

 a lighter compact limestone. 



Some layers were also found with compact sandstone which cleaxes 

 in more or less even slabs, and is therefore used for flagstones. 



Hitherto fossils and clear trail marks have only been found in the 

 lower beds on the north-western side of Kroksund. 



The upper part of the series forms — as already mentioned — the 

 steep thickly wooded slope of the mountain right up to the precipice 

 of porphyry, which crowns the whole series. The uppermost beds are 

 covered with a mighty talus, formed for the most part of blocks which 



