4 P. A. ØYEN [No. 6 



rather a deposit of submarine morainic material. On the very 

 bottom of the clay-pits numerous stones and blocks were seen, 

 not rare ly attaining a transverse section oi' about a couple of 

 metres. These blocks and stones are to be regarded as residua! 

 ones from the different layers of clay as no special stone-layer 

 could be observed from which they might have derived. In this 

 erratic material blocks of a reddish-grey colour representing the 

 different varieties of syenite that is to be found as a solid rock 

 to the north of Chritiania played a most prominent part, but 

 also stones and blocks of a dark colour were seen representing 

 different varieties of crystallme rocks from the central part of 

 Norway. The rich occurrence of Tussilago farfara Lin. bears 

 a strong testimony as to the chemical composition of the bluish- 

 grey and grey or even yellowish-grey clay overlying the bottom- 

 layer as of the bottom-layer itself. This bottom-layer, as a mo- 

 rainic one, hat) a somewhat variable thickness filling up the 

 hollows and cavities of the underlying rock surface. 



II. Directly overlying this bottom-layer is a tough and soft 

 clay of bluish or bluish-grey colour. The thickness of this clay 

 stratum is about one meter and the clay itself proves to be the 

 deposit of a rather deep water having been crowded with a 

 number of mollusca now being found as fossils in the clay, 

 such as : — 



Nucula tennis Mont. forma typica. 



Leda pernula Mull. 



Portlandia lenticula Moll. Length 5,5 mm. This species 

 often occurs in complete specimens, and it is very numerous. 



Area glacialis Gray, forma typica, of quite the same type 

 and size as has also been found to be the leading fossil of the 

 lovver layers in the clay-pits of the brick-work of Svenengen in 

 the eastern part of Christiania. 



Axinus flexuosus Mont. 



Abra longicallis Sc. 



Saxicava pholadis Lin. This species occurred in a juve- 

 nile type being represented by thin and small specimens. 



Siphonodentalium vitreum Sårs. 



