EVIDENCES OF VOLCANIC ACTION 13 
boniferous age are met with too, well characterized throughout by 
fossil fauna. The central part of the island, as tested in the upper 
parts of south running flat river valleys, is built up by mesozoic 
sediments; the Malakatyn hills covered by quaternary sediments 
are their culminating point. Only on few points beneath this cover 
tertiary sediments are preserved. The discovery of mesozoic strata 
of various ages explains the finding of ammonites by Hedenström 
during his stay on the island in the former part of the past century 
and whose report hereupon caused later on lively controversies. 
The whole region is strongly faulted, partly by concentric step 
faults, the Nerpalakh bay on the westcoast of Kotelnyi representing 
a circular stepfault, and partly by radiating faults; this circumstance 
explains the fact, that palaeozoic rocks are encountered only along 
the shores, while the mesozoic strata, also strongly faulted and 
turned up by faulting, build up the central part of the island. In 
this central part dikes of a glassy sodaliparite cut through the 
mesozoic strata forming low smothed hills in some river valleys. 
The relations of this volcanic to the tertiary strata are unknown. 
The rock is light gray, without coloured constituents, containing 
phenocrysts of quartz and twinned plagioclase feldspar in the glassy 
groundmass, and in steam cavities infiltrations of secondary silica 
(opal and chalcedony) are abundant. In the neighbourhood of these 
dikes an erratic boulder of a finegrained bright reddish granite 
rich in quartz was met with. Erratic pebbles of this sodaliparite 
were found also on the islands of New Siberia and Thaddaeus. 
The basalts of the opposite mainland are mentioned by Suess; 
they cut through a gray granite and represent a magmabasalt type, 
tich in brown glass, phenocrysts of olivine and pyroxene, the feld- 
spars almost quite wanting. Pebbles of basalt are represented from 
the greater Liakhoff Island. 
The continental backland is covered with quaternary and modern 
fine grained river deposits, the next step of connection being the 
north slope of the Kharaulakh range on the point where this range 
