﻿SUMMARY OF THE CONTENTS. 685 



during the formation of the ra itself. A corresponding yoldia 

 clay is known in the Western part of Sweden. 



Pp. 116—123. The Oldest Area Clay of the 

 Kristiania Region. 



The precipitation of the glacier-silt outside the ra has now 

 further continuously deposited on the upper yoldia clay the above- 

 mentioned older area clay. From the older yoldia clay to the 

 upper yoldia clay, and from this again to the oldest area clay, 

 I have found all possible transitions. Several forms of the 

 fauna are common to the two last mentioned clays (such as 

 yoldia hyperborea, macoma calcaria, etc); but most species 

 are new and characteristic of the area clay, and are never found 

 in the yoldia clay, wliereas the leading species of these strata, 

 the portlandia arctica is never found in the overlying area 

 clay. 



The predominant leading forms of the fauna of the oldest 

 area clay, which comprises about 20 forms (see pp. 117, 118), 

 are the following 4 species : 



area glaeialis, Gray, portlandia lenticula, Fabr., siphono- 

 dentalium vitreum, M. Sårs, antalls striolata, Stimpson. They 

 are all of them high arctic species, in the Polar Sea found only 

 at a considerably greater depth. The fauna of the oldest area 

 clay has therefore probably lived at the depth of about 80 — 100 

 metres. As these clay strata are only a few metres thick, and 

 are found exclusively outside the ra, up to about 25 — 40 m. (at 

 Sandefjord; see p. 670) above the modern sea-level, vve must 

 conclude that the land at the ra, immediately after the conclusion 

 of its formation, had been sunk to about 100 — 125 m. lower 

 than it is at present. A corresponding area clay is known in 

 Bohuslån, Sweden. 



On pp. 124 — 131 are described yoldia clay and area clay 

 from the environs of Trondhjem and from Nordland. Among 

 the species of the mollusca of the yoldia clay from the Trond- 

 hjem region are some that are not known in the yoldia clay of 



