﻿684 SUMMARY OF THE CONTENTS. 



B. The Younger (Upper) Yoldia Clay and the Oldest 

 Area Clay. 



Pp. 111 — 116. The younger (upper) yoldia clay. The 

 sections of the clay-beds in the brickfields along the river Glom- 

 men shows at Valle & Evje the following profiler (1) in the 

 lowest part of the profile immediately on the scratched floor, the 

 older yoldia clay with the fauna mentioned on p. 22; (2) 

 upon this clay, strata of a younger yoldia clay and (3) upon that 

 again, strata of the oldest area clay are continuonsly deposited. 



The fauna of the younger yoldia clay comprises partly the 

 same species as the older yoldia clay, hut in other varieties; 

 some new forms have also supervened (see p. 112). Thus for 

 instance, porilandia arctica in the older clay reaches a length of 

 27 — 28 mm., in the younger only about 18 mm. Macoma cal- 

 caria in the lower clay attains as much as 52 mm., hut in the 

 upper yoldia clay is only 42 mm. long. In accordance with 

 well known experiences regarding the relation between the size 

 of the high arctic species and the climate (temperatiire of sea- 

 water, etc.) this indicates the beginning of an amelioration of 

 the climate during the deposition of the upper yoldia clay. 



Further, it is to be remarked that this clay must have been 

 deposited at some greater depth than the older yoldia clay, as 

 is indicated by the change in the fauna; among the new forms living 

 at some considerably greater depth, yoldia hyperborea, Loven 

 may especially be mentioned. On the other hand, the charac- 

 teristic deep-water forms of the area clay are still wanting. It 

 is thus probable that the fauna of the younger yoldia clay must 

 have li ved at a depth of about 40 — 60 metres (instead of the 

 10 — 30 metres found in the case of the fauna of the lower 

 yoldia clay). As the strata of the younger yoldia clay have a 

 thickness of only 1 — 2 m., it is obvious from the above-mentio- 

 ned circumstance that these strata are deposited during a conti- 

 nual sinking of the land; and as also the younger yoldia clay 

 occurs immediately in front or at side of the ra, this sinking 

 during the deposition of the yoldia clay must have continued 



