411 
partly to tidal action and currents which may transport many small 
young ones along the sea-bed, and especially at steep shores bring 
them out at depths where they are not able to live. It can not 
at present be decided to which depth the adult Mya truncata reach, 
as their habit. of burrowing prevents their being easily procured by 
means of the dredge or trawl. — J. Sparre Schneider has for- 
merly dråwn the attention to the probability that young specimens 
of the Mya-species may occur at greater depths than the adult 
ones 1), 
In a letter partly published in Professor W. Brøggers work: 
»Nivåforandringer i Kristianiafeltet" p. 106 & 107, Mr. A.S. Jensen 
suggests that a former sinking of the seabed off the Færoe-Islands 
has taken place. His views are as follows: ,,0n the banks near 
the Islands whole layers of an extinct southern fauna are deposited : 
Årca tetragona, Pectunculus glycemeris, Venus casina, Tellina crassa, 
Tapes edulis. At the Norwegian coasts these species reach at most 
50 fms., but the bank on which the principal part of the shells 
occurred (more than 100 of AÅrca tetragona) is 150 fms. below the 
sea-level",. Im this case there is a probability thåt several 
shells are deposited considerably below the level where the animals 
lived. j 
Professor Brøgger, however, has seen that the named occur- 
rence of littoral shells at great depths is a more common pheno- 
menon than the Naturalists who have formed the mentioned sinking 
hypotheses . have supposed. He has perceived that masses of dead 
shallow-water shells. have been recorded from relatively great depths 
along the Norwegian west-coast, and he refers to similar oceurrences at 
Færoes, the Shetland Isles, and Rockall, as well as to the dredgings 
of Godwin Austen west of Ireland 1849. Professor Brøgger now 
concludes that these littoral shells from considerable depths originate 
from the same period during which the sea-bed was uplifted 100 to 
1) J. Sparre-Schneider: Undersøgelser af Dyrelivdt i de arktiske 
Fjorde. ILL. Tromsø Museums Aarshefter. VIII & IX. p. 
