401 
in the Atlantic, and in tlie Mediterranean ^), what may be presumed 
mainly to depeud on the different bottom-temperature of these seas. 
In most parts of the North Polar Basin the bottom temperature is 
0 to -p 2° C., in the Atlantic (below 1000 fathoms) 1° to 4°, and 
in the Mediterranean (below 200 fathoms) 12°—L4°. In order to 
give a feAv examples, two of the dead shallow-water shells from the 
depths of the North Polar Basin: Saxicava arctica L. and Tellina 
calcarea Chemn. may be mentioned. Both these species are known 
in a li ving 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. Priele & Grieg 1901 1. 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. ^) (A. S. Jensen 1900 1. c.) 
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. 
0 Also in different parts of the same ocean there can be a great diffe¬ 
rence as to the vertical range of the molluscs, if the hydrographical 
conditions are not uniform. 
2) G. O. Sars; „Mollusca regionis arcticæ Norwegiæ“. Christiania 1878. 
D. van Haren Noman: „Die Lamellibranchiaten gesammelt wahrend 
der Fahrten des „Willem Barents“. Niederlandisches Archiv flir Zool. 
Suppl. Bd. Leiden 1881. 
■*) This depth will probably prove to be too little, at least off the North 
of Iceland. 
Vidensk. Meddel, fra den naturh. Foren. 1902. 
26 
