﻿706 SUMMARY OF THE CONTENTS, 



with rude, unpolished flint implements lived at the time of the 

 upper tapes-banks. The land at Kristiania must at that time 

 have lain about 35 — 40 metres lower than it lies at present 

 (see pp. 449—452). 



On the westcoast of Norway upper tapesbanks are known 

 at the lake Gravensvand in Voss (452—454), etc. A number of 

 shell-banks belonging to this group are known in the environs 

 of Trondhjem (pp. 454. 455). 



The occurrence of shell-banks from this period also as far 

 north as at Vardø (p. 456) is interesting. A tapes-bank here 

 contained 26 species, of which only 3 were arctic, whereas 11 

 species were boreal, and no less than 12 lusitanic. A number 

 of these south ern forms are at present extinct in this northern 

 region, — a still further proof that the climate has been milder 

 during the time of the upper tapes-banks than it is to-day. 



Pp. 457 — 473. 4. The Isocardia clay of the Kristiania Valley. 



Gorresponding with the upper tapes-banks, there is, in 

 the lower parts of the Kristiania Valley, up to 55 — 60 (?) m. 

 above the sea, a widespread shellbearing clay, the isocardia 

 clay, so called from its leading fossil, isocardia cor, Lin. A 

 number of occurrences from the Kristiania Valley are enume- 

 rated on pp. 459. The composition of the fauna of this clay 

 will appear from the table, pp. 460, 461; 82 species of mol- 

 lusca are known in all, of which 11 are arctic, 38 boreal, and 

 33 lusitanic, or in the proporhon : -!- | a : + f 6 : -i- f ^, i. e. nearly 

 the same as for the contemporaneous upper tapes-banks. To 

 the species mentioned on pp. 460, 461 the five species enume- 

 rated on pp. 464, may probably be added, from an occurrence 

 at Langvik, Bygdø, near Kristiania (see table, pp. 463). The 

 entire known fauna of the isocardia clay at Kristiania would 

 thus comprise 87 species, of which 12 are arctic, 40 boreal, 

 and 35 lusitanic. 



The following are the more common species: ostræa edulis, 

 pecten septemradiatus, p. tigrinus, cardium edule, c. echina- 

 tum, isocardia cor, cyprina islandica, astarte elliptica, a. 



