106 The American Geologist. March, 1902 
Later, changes of the mollusca inhabiting the sea in the 
Christiania valley during the formation of the several marginal 
moraines, marking successive pauses of the retreat of the ice 
boundary, enable our author to distinguish six successive 
faunal conditions, passing more or less definitely from one to 
another, as follows: 
1. The older Yoldia clay, deposited on the present sea 
bed near the shores and on the land to the outermost moraine 
ridge, denoting a gradual sinking of the land from 50 meters 
or more above its present level to about 30 meters below that 
level. 
2. The younger Yoldia clay, only one to two meters thick, 
belonging to’ the later part of the time of formation of the 
outer moraine, denoting subsidene to about 75 meters lower 
than now. 
3. The oldest Arca clay, a few meters thick, also found 
exclusively outside the outer moraine, proving a continued 
sinking until the land was depressed 100 to 125 meters lower 
than it is at present. 
4. The middle Arca clay, of deep water, and the older 
Portlandia clay, of less depth, forming together a very thick 
deposit between the outer or first and the second series of 
marginal moraines, which are twelve to fifteen mules apart. 
At the time of its deposition the land was at least 150 meters 
lower than now; and the temperature of the sea, though still 
arctic, Was somewhat warmer than in the preceding stages. 
5. The younger Arca clay, much worked for brickmaking” 
in the Christiania valley, deposited between the second series of 
moraines and the third great series, showing a further moder- 
ation of the sea temperature and a continuance of the sub- 
mergence. At the same time, the younger Portlandia clay, 
representing less depths of water, was spread also outside the 
third moraine series, at altitudes of 100 to 175 meters above 
the present sea level. 
6. The Lophelia fauna, occurring on a dead coral reef at 
Drébak, south of Christiania, belonging to a somewhat warmer 
sea at the stage of maximum submergence, when the highest 
shore line, there 180 meters above the present shore, was 
formed. This fauna is believed to have been contemporaneous 
with the fifth station of recession of the ice-sheet, called the 
