402 
The greatest depths recorded for 7'e//ina calcarea in the North 
Polar Basin are as follows: 
Between Norway & Spitzbergen (Temp. above 0? C.) 
197 fms. (Friele & Grieg 1901) 
Barents-Sea (Temp. below 0? C.) 148 — ( — FE Å 
Jan Mayen, East-Greenland (Temp. below 0? C.) 
40 fms. (A: C, Jensen 1900 1. €.) 
On the other hand, from the Atlantic the species has been 
recorded living at a depth of 1255 fms."), 
Then it seems fairly reasonable to infer that it is the extre- 
mely low temperature at the bottom of the Arctic sea which pre- 
vents these species from reaching the great depths. : 
As there is now evidence of a higher temperature in the Arctic 
sea in post-tertiary time,'e. g. in the shellheaps with Cyprina 
islandica and Littorina littorea in Spitzbergen?), and the deposits 
at the Northern coasts of Russia with Cardium edule?), the idea 
presents itself that such species as the named, in more temperate 
periods, possibly have reached far greater depths than they do at pre- 
sent. According to my opinion there is no reason why the shallow- 
water shells should not have lain on the bottom of the sea from such 
temperate periods. I admit, however, that the presence of all the 
dead shallow-water shells in the depths of the North Polar. Basin 
can not be explained in this way. Several of the found species 
live nowhere at considerable depths, and species like Margarita 
helicina Phipps, and Lacuna crassior Mont. are in the main restricted 
to the vegetation zones, as they are vegetable-feeders; but there 
is every reason to maintain the view that the occurrence of 
1y A. E. Verrill: ,Results of the Explorations made by the steamer 
»Albatross"" etc. United States Commission of Fish and Fisheries. 
Report for 1883. Washington 1885. p. 575. (The species is here 
mentioned as Macoma sabulosa (Spengl.) Mårch.) 
2) A. G. Nathorst: ,Jordens Historia". Bd. IL 
SØEN: SES ANE Zur Kenntniss der geologisehen Geschichte der 
Fauna des Weissen- und des Murman-Meeres.  Verh. Kais. Russ. 
Mineral. Gesell. ng Petersburg. 2. Ser. Bd. 38. N. 1. 1900: 
