433 
It is hardly known at present if the fishes sometimes ejeet the 
shells in a perfect state. In all probability this, however, is the 
case. Thus it is very common to find perfect shells in the stomach 
of several flat-fishes, e. g. in Drepanopsetta platessoides and 
Pleuronectes limanda, and even in the common plaice, which as a 
rule crush the shells, small perfect specimens (as Margarita helicina, 
Lacuna divariata, etc.) may not uncommonly be found. Mr. R. 
Hørring has made the observation that even so good sized a form 
as the grown-up Yoldia limatula can be found undamaged in the 
stomach of Pleuronectes limanda !"). 
If in a certain area a sinking of the seabed has really taken 
place there must follow a series of continuous local-faunas or 
biological groups, which have displaced one another gradually, 
while the sinking has continued. Still, no such a series of bio- 
logical groups from various levels has been pointed out anywhere at 
the alleged sinking places. If, on the contrary, aå transportation 
of the shells has taken place, we can only expect from the higher 
levels to find fragmentary biological groups. 
Suppose that we would try to settle whether the specimens of 
Littorina obtusata, found at St. 9 (165 fms.), west of Ireland, have 
been derived from another place or not; it would then be desirable 
to elucidate by dredgings at the same place whether all the bio- 
logical groups: from the tract between tide-marks (Littorina obtu- 
sata, L. littorea, L. rudis, Purpura lapillus, Åcmæa testudinalis, 
Mytilus edulis, etc.), from the Laminarian zone, from the Coralline 
zone, etc., really occurred there or not. 
According to our present state of knowledge with regard to the 
shell-deposits and the shell-transportation the following explanation 
of the phenomenon treated here may be set forth as the most 
1) R. Hørring: ,Rapport om Fiskeriundersøgelserne under Færøerne 
og Island i Sommeren 1901". Fiskeriberetning for Finansaaret 1900 
—1901. Kjøbenhavn 1902. 
Vidensk. Meddel. fra den naturh. Foren. 1902. 28 
