Glacial Changes in Christiania. 323 



lie referred to the concluding part of the period of subsidence rather 

 than to that of elevation. They are overlaid by gravels with 

 nuinerons large boulders. 



The higher, late Glacial shell beds in the vicinity of Christiania 

 have long been known through the rlescriptions given by Keilhau, 

 M. Sars, and Kjerulf. They consist, for the most part, of sands and 

 pebbly gi-avels, crowded with fragments of broken shells, and in 

 some places entire forms, belonging to the littoral or the highest 

 part of the laminarian zone, which lived at depths not more than 

 about 10 metres. They are known as the Mya-beds, from llya 

 truncata, one of the most characteristic forms ; Mytilus edulis is also 

 common; other species are Cyprina islandica, Macoma haltica, 

 Littorina Uttorea, etc. In the southern part of Smalenene, to the 

 south-east of Christiania, the upper Mya-beds contain 23 species of 

 mollusca, 17 of which are Arctic and 6 boreal forms. The beds are 

 situated at levels of 130-155 metres above the sea. In the lower 

 Mya-beds, near Fredrikshald in the same district, 45 species of 

 mollusca are known ; of these 22 species are Arctic, 20 boreal, and 

 3 Lusitanian. In the same beds near Christiania, at 110-140 m. 

 above the sea, 26 species of molkisca are known, 9 of which are 

 Arctic, 13 boreal, and 4 Lusitanian. 



A series of fossiliferous clay-beds, corresponding with the Mya- 

 beds of the higher or early stages of the uplift, are found in the 

 Christiania valley, and are known as the Mytilus-Cyprina-clays. 

 At Grorud lower and younger clays occur, containing a number 

 of southern (Lusitanian) species, including Pliolas Candida, Cardiim 

 ednle, etc. ; they are known as the oldest Cardium-clays. 



From differences in the character of the shell beds in various 

 localities, at levels corresponding to the same percentage of the total 

 uplift, it would appear that the elevation of the region began earlier 

 in the southern peripheral portions once covered with the ice-sheet, 

 and continued in advance of that of the central portions, at least 

 during the first half of the uplift. 



III. The Post- Glacial Shell Beds and Clay Deposits of the Christiania 



Begion. 



Shell beds, lower and younger than the Mya-beds, corresponding 

 to the middle period of the uplift, that is, from 40 to 66 per cent, 

 of the total elevation of the land, are somewhat rare, and it is 

 therefore difficult to fix a definite boundary between the late Glacial 

 and the post-Glacial deposits, but it is probably situated at a level 

 of something over half (50-60 per cent.) of the total uplift. 



At Bryn, near Christiania, there is a younger Cardium - clay, 

 corresponding to the middle period of the uplift, the fauna of which 

 has been described by Crosskey & Eobertson. It contains 15 

 species of mollusca, only 1 of which is Arctic, whilst 7 are boreal, 

 and 7 Lusitanian species. The beds are now 76-85 m. above the 

 sea, and the shells probably lived at depths of 20-30 m. The highest 

 marine shore-line here is 215 metres. 



During the later stages of the uplift of the land, beds of shells 



