403 
de ad shallow-water shells in the depths of the North 
Polar Basin partly (and mainly) may depend on transport, 
and possibly partly on altered hydrographical conditions. 
I have here tried to show that the objections set forth against 
explaining the occurrence of dead littoral shells at the great depths 
of the Arctic sea as a result of shell-transportation really are rather 
uniinportant. The question might now be raised whether more 
serious objections can be set up against the explanation of the 
phenomenon by the theory of a former siiiking of the seabed. The 
most iraportant objections are undoubtedly those which take their 
rise from an investigation of the bottom-deposits. Such investiga- 
tions have been carried out by O. B. Bøggild with the results 
that great sinkings between Jan May en and Iceland are extremely 
improbable ^). In this place I shall only call the attention to a few 
features concerning the molluscs which, without being of great im¬ 
portance, still may be of interest to discuss. 
1) Friele states, that several of the littoral shells, found at 
great depths off Spitzbergen, were fresh. Now it is, to be sure, 
frequently impossible to decide whether a shell is fresh or thousands 
of years old. A shell may in a few years get a completely fossil 
appearance, but that a fossil shell, on the contrary, has a fresh 
appearance is a much rarer phenomenon. 
2) The number of littoral Lamellibranchia-species at each of 
the 11 stations, where Ingolf dredged the shallow-water shells be¬ 
tween Jan Mayen and Iceland, is too small supposing that the 
trawl has worked in a sunken littoral seabed. At one station 
occurred 5 species, at four stations 2 species, and at 6 stations 
1 species, or consequently not even 2 species on an average at 
each station. If we trawl in the littoral zone in the North Polar 
Basin such a small number will not present itself. The Norwegian 
North-Atlantic Expedition dredged on an average 4 to 5 species 
of Lamellibranchiata at 8 stations in the littoral zone, between 0 
O. B. Bøggild; „Om en formodet Sænkning af Havbunden mellem 
Island og Jan Mayen“. Vid. Medd. Naturh. Foren. Kjøbenhavn 1902. 
26* 
