Glacial Changes in Christiania. 319 



consist of enormous masses of stratified sand and gravel of rolled 

 pebbles, with patches of clay, which have been brought down by 

 the streams produced by the melting ice and deposited beneath the 

 sea-level immediately in front of the glacier. In structure they may 

 be compared to dsar, but their position is that of terminal moraines. 

 The outermost ra crossing the Christiania fjord has been assumed to 

 represent the furthest extension of the land-ice during the last 

 glaciation of the country, but this is incorrect, for the rock surfaces 

 beyond the ra are glacially striated in the same way as tliose behind 

 it, and there is no doubt that the ice of the last glaciation reached 

 outwards, beyond the present shore limits of the country. 



Outside the terminal ra, that is, between the moraine and the 

 coastline, but never within the morainic barrier, there is a widely 

 spread deposit of clay, known as the Yoldia-clay, which in places 

 rests directly on the striated surfaces of the ancient rocks and in 

 places on the outer slopes of the ra, from below the present sea-level 

 to 40-45 metres above it. The clay consists of a fine mud, often 

 with stones and boulders of porphyry, syenite, and granite, 

 originating from the central and northern portions of the Christiania 

 region ; many are typically striated. Molluscan shells of large size, 

 indicating favourable conditions of existence, are abundant in the 

 clay. Twenty-six species have been determined ; the commoner and 

 most characteristic forms are Portlandia (Yoldia) nrctica, Gray, 

 Macoma cnlcaria, Chem., Saxicava arctica, Linn,, Zeda pernula, Miill., 

 and Nucula tenuis, Mont. The first of these occurs nearly everywhere ; 

 both valves are usually found united, and the epidermis and ligament 

 are preserved. In places the clay contains numerous foraminifera ; 

 one species, Folystomella arctica, Park. & Jones, is a typically Arctic 

 form. The mollusca of the Yoldia-clay are now all found living in 

 high Arctic regions at depths of 10-30 metres ; most of them are 

 present in the Kara Sea, and it may reasonably be assumed that 

 these fossils lived under similar conditions of depth and temperature 

 as their recent representatives. The Yoldia - clay with its 

 characteristic fauna can be traced on the sea-bottom round the 

 coast of South Norway to depths of over TO fathoms, which shows 

 that during the earlier deposition of the clay the land must have 

 been at a higher level than at present. The shells appeared to have 

 lived contemporaneously with the formation of the outer ra, and the 

 land appears to have sunk during this period from about 50 metres 

 above to 70-75 m. below the present level. 



The question of the elevation of the land in Norway before the ra 

 period, during the time of the great glaciation, is discussed by the 

 author in connection with the occurrence of sub-fossil shells, of 

 species which, living, are found at depths of only a couple of 

 fathoms, in the sea between Norway, Spitzbergen, and Greenland, 

 where they occur at depths of 20-500 fathoms. Further, dead 

 shells of shallow-water forms like Portlandia arctica have been 

 dredged up from depths of 656-1333 fathoms off Spitzbergen, where 

 they are associated with numerous otoliths of fishes. Dr. Nansen 

 agrees with the author that these dead shells are distributed over too 



