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On the hypotheses on the sinking of sea-beds 
based on the occurrence 
of dead shallow-water shells at great depths in the sea. 
By 
A. 0. Johansen, M. Sc. 
Åt aifferent times it has been noted by naturalists that dead 
shallow-water shells. have been found at much greater depths than the 
living molluscs of the corresponding species. The question how this 
phenomenon as a rule is to be explained has of late got a peculiar 
interest since several authors have tried to make this occurrence 
the foundation for the belief that great sinkings of the sea-bed have 
taken place in post-tertiary time at different parts of the earth. 
If we look at the phenomenon from a theoretical point of view 
three hypotheses may be set forth to its explanation: 
1) A transportation of the shells by means of floating ice, currents, 
organisms, etc., may have taken place. 
2) A sinking of the seabed may have occurred. 
3) At an earlier period the species in question may have had 
another vertical distribution than at the present time. 
It must be considered that we in some cases, perhaps, may 
have to look for one, in other cases for another of these explana- 
tions. 
Most of the authors who have called attention to the disere- 
pancy in the distribution of the living molluscs and that of the 
dead shells have regarded it as merely a local phenomenon; but if 
