VIII.] THE TUNDRA. 287 



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 dejDth 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 

 in rich abundance, and along with them masses of old drift- 

 wood, originating from the Mammoth period, known by the 

 Russian natives of Siberia under the distinctive name of 

 " Noah's wood." Besides there are to be seen in the most 

 recent layer of the Yenesej tundra, considerably north of the 

 present limit of actual trees, large tree-stems with their roots 

 fast in the soil, which show that the limit of trees in the 

 Yenesej region, even during our geological j^eriod, went further 

 north than now, perhaps as far as, in consequence of favourable 

 local circumstances, it now goes on the Lena, 



On the slopes of the steep tundra bank and in several of the 

 tundra valleys there is an exceedingly rich vegetation, which 

 already, only 100 kilometres south of Yefremov Kamen, forms 

 actual thickets of flowering plants, while the tundra itself is 

 overgrown with an exceedingly scanty carpet, consisting more of 

 mosses than of grasses. Salices of little height go as far 

 north as Port Dickson (73° 30' N.L,), the dwarf birch {Betida 

 nctna, L.) is met with, though only as a bush creeping along the 

 ground, at Cape Schaitanskoj (72° 8' N.L.) ; and here in 1875, on 

 the ice-mixed soil of the tundra, we gathered ripe cloudberries. 

 Very luxuriant alders {Alnaster fruticosus, Ledeb.) occur already 

 at Mesenkin (71° 28' N.L), and the Briochov Islands (70° to 

 71° N.L.), are in several places covered with rich and luxuriant 

 thickets of bushes. But the limit of trees proper is considered 

 to begin first at the great bend which the river makes in 



^ As specimens of the sub-fossil mollusc fauna of the tundra some of 

 the common species are delineated on page 288. These are : — - 



1. Mya arenaria^lAn. § of natural 9. Fusua fornicatus, JieQYe. i. 



size. 10. Fusus tomatus, Gould. |. 



2. Mya truncata, Lin. var. Udde- 11. Margarita elegantinsima, Bean. 



raUensh, Forbes, f . Natural size. 



.3. Sn.ricava pholadis, Lin. §. 12. Pleurotorim piicifera, Wood. 



4. Tellina lata, Gmel. f. Natural size. 



5. CardhancHiatum, Fabr. §. 13. Pleuroioma j^f/rcimidalis, Strom. 

 G. Leda peruuIa,'Mu\\. vav.buccata, 1^. 



Steenstr. Natural size. 14. Trichntropis horeal'm, Brod. H. 



7. A^Mc«/rteay««sa, Reeve. Nat. size. 15. Natica hclicoides, Johnst. Nat. 



8. Fnsus Kroyeri, Moll, f . size. 



