378 
THE VOYAGE OF THE VEGA. 
[chap. VIII. 
is formed of loose, earthy layers, is also quite low and often 
marshy, while on the other hand the eastern strand consists of 
a steep bank, ten to twenty metres high, which north of the 
limit of trees is distributed in a very remarkable way into 
pyramidal pointed mounds. Numerous shells of Crustacea 
found here, belonging to species which still live in the Polar 
Sea, show that at least the upper earthy layer of the tundra 
was deposited in a sea resembling that which now washes the 
north coast of Siberia.^ 
The tundra itself is in summer completely free of snow, but 
at a limited depth from the surface the ground is continually 
frozen. At some places the earthy strata alternate with strata 
of pure, clear ice. It is in these frozen strata that complete 
carcases of elephants and rhinoceroses have been found, which 
have been protected from putrefaction for hundreds of thousands 
of years. Such finds, however, are uncommon, but on the 
other hand single bones from this primeval animal world occur 
high, and the left low. The cause of this is the globular form of the 
earth and its rotation, which gives rivers flowing north a tendency towards 
the east, and to rivers flowing south a tendency to the west. This tendency 
is resisted by the bank, but it is gradually eaten into and washed away by 
degrees, so that the river bed, in the course of thousands of years, is 
shifted in the direction indicated. 
1 As specimens of the sub-fossil mollusc fauna of the tundra some of 
the common species are delineated on the opposite page. These are ; — 
1. My a arenaria, Lin. f of natural 
size. 
2. Mya truncata, Lin. var. Udde- 
vallensis, Forbes, f. 
3. Saxicavapholadis, Lin. 
4. Tellina lata, Gmel. f. 
5. Cardiuni ciliatum, Fabr. f. 
6. Leda permda, Miill. var. buccata, 
Steenstr. Natural size. 
7. Nucula expa7isa,lleQyG. Nat. size. 
8. Fusus Kroyeri, Moll. f. 
9. Fusus foiiiieatus, Reeve. 
10. Fusus tornatus, Gould, f. 
11. Margarita elegantissima, Bean. 
Natural size. 
12. Pleurotoma plicifera, Wood. 
Natural size. 
13. Pleurotoma pyramidalis, Strom. 
IJ. 
14. Trichotropis borealis, Brod. 1^. 
15. Natica Jielicoides, Johnst. Nat. 
size. 
