J. Croli— Arctic Interglacial Periods. 305 
Evidence from Shells.—In the freshwater deposits in which 
the bones of the Mammoth are found, there are fresh-water and 
land-shells, which indicate a warmer condition of climate. I 
quote the following from Mr. Howorth’s memoir :— 
“Schmidt found Helix Schrencki in fresh-water deposits on 
the tundra below Dudino and beyond the present range of trees. 
patim found recent shells of it, with well-preserved colors, 
9° farther south, in lat. 68° and 69°, within the present range 
of trees, at the mouth of the Awamka. The most northern 
limit hitherto known for this shell was in lat. 60 .. where 
ore found by Maak in gold-washings on the Pie”. 
stoi Noss, but no farther. Pisidium fontinale still lives in the 
Pools on the tundra; as does Succinea puiris on the branches 
of the A lnaster on the Brijochof Islands.” 
lr, Belt mentions* that the Oyrena fluminal’s is found in 
Siberia in the same deposits which contain the remains of the 
Mammoth and the Rhinoceros tichorhinus. a 
he evidence, then,” says Mr. Howorth, “of the débris of 
Vegetation, and of the fresh-water and land-shells found with 
the Mammoth-remains, amply confirms the @ priori conclusion 
that the climate of Northern Siberia was at the epoch of the 
Mammoth much more temperate than now. It seems that the 
botanical facies of the district was not unlike that of Southern 
Siberia, that the larch, the willow, and the Alnaster were prob- 
ably the prevailing trees, that the limit of woods extended far 
to the north of its present range and doubtless as far as the 
Arctie Sea; that not only the mean temperature was much 
higher, but wt ts probable that the winters were of a mpelae and 
* Quart. Journ. Geol. Soc., vol. xxx, p. 464. 
