401 
in the Atlantic, and in the Mediterranean"), what may be presumed 
mainly to depend on the different bottom-temperature of these seas. 
In most parts of the North Polar Basin the bottom temperature is 
0 to — 29 C., in the Atlantic (below 1000 fathoms) 1? to 4%, and 
in the Mediterranean (below 200 fathoms) 12?7—149, In .order to 
give a few examples, two of the dead shallow-water.shells from the 
depths of the North Polar Basin: Saæicava arctica L. and Tellina 
calcarea Chemn. may be mentioned. Both these species are known 
in a living state from the Atlantic at much greater depths than 
from the North Polar Basin. The greatest depths recorded for 
Saxicava arctica in the North Polar Basin are as follows: 
Off Lofoten (Temperature above 0? C.,) 
down to 300 fms. (G. O. Sars)?”) 
Between Norway and Spitzbergen (Temp. above 0? C.) 
down to 191 fms. (H. Friele & Grieg 19011. c.) 
Between Norway and Spitzbergen (Temp. above 0? C.) 
down to 192 fms. (D. van Noman)) 
Barents-Sea (Temp, below 0? C.) 
down to 160 fms. (Noman 1881 1. c.) 
North of Iceland, Jan Mayen, East-Greenland | 
down to 40 fms.7) (A. S. Jensen 1900 1. é.) 
On the contrary in the Atlantic this species reaches in all 
probability depths of more than 1000 fms. The greatest depth, 
however, from which I have seen recent specimens — with 
remainders of the animals — (in British Museum, Natural History) 
is 808 fms. 
") Also in different ske of the same ocean there can be a great diffe- 
rence as to the vertical range of the molluses, if the hydrographical i 
conditions are dn uniform. 
?) G. 0. Sars: ,Mollusca regionis arcticæ Norwegiæ". Christiania 1878. 
3) D. van Haren Noman: ,Die Lamellibranchiaten gesammelt wåhrend 
der Fahrten des , Willem Barents". Niederlåndisches Archiv fir Zool. 
Suppl. Bd. Leiden 1881. 
1) This depth will probably prove to be too little, at least off the North 
of Iceland. 
Vidensk. Meddel. fra den naturh. Foren. 1902. 26 
