50 GEOLOGICAL MEMOIRS. 
tinues even into the basin of the Lena. M. von Middendorff found 
no trace of the chalk formation, and I have expressed the opinion 
that the Jura beds of Siberia, like those of the Petschora land, are 
covered immediately by the tertiary deposits, which have such an 
enormous extent along the Icy Sea, and have been very attentively 
observed by our traveller. That these tertiary beds, containing the 
remarkable Adam’s-wood or Noah’s-wood, with perfect skeletons of 
Mammoths, have only recently for the first, or perhaps the second 
time, emerged from the sea, is most distinctly shown, by their in- 
cluding, up to a certain height, and for a considerable distance from 
the shore, well-preserved shells of mollusca still livmg in the Arctic 
Sea. 
Regarding the age of the beds forming the Taimyr or Bynanga 
Mountains no decided opinion can be formed, no organic remains 
having been found in them. Still their mineralogical character, the 
mode of their occurrence, and some other marks, place them without 
doubt in one of the most ancient periods in the formation of the 
earth. Further inquiry must also decide the age of the clayslate, 
greywacke, limestone, dolomite and sandstone, observed by M. von 
Middendorff on his journey from Jakutsk to Udskoi and the Schantar 
islands, and in the basm of the Amur. Still more interesting are a 
whole series of crystalline, eruptive rocks seen in various parts of _ 
Eastern Siberia, and among which we find trachyte for the first time 
in this region of the globe. , 
[J. N.] 
