LOWER AND UPPER SILURIAN GROUPS CLEARLY DEFINED. 19* 
laintainable, a natural separation into Lower and Upper groups might generally 
he looked for in other countries, where strata of this age prevailed*. In Scan- 
dinavia, indeed, the identity of two such groups with the British types is not only 
most striking, but even many of the subordinate details in both countries are to a 
lemarkable degree analogous. 
Hating now sufficiently defined the dawn of palaeozoic succession, and our 
aders being, we hope, convinced, that the Lower Silurian rocks constitute the 
arliest-foimed sediments in which animal life has been discovered in tracts where 
the series, void of all animal remains in its lowest stratum, rests on crystalline rocks, 
ley will now pioceed to the consideration of the successive deposits of Russia 
with a clear idea of the earliest stages in the long series of deposits that we are 
about to describe. 
See Load. and Edmb. PM. Mag., 1835. p. 46. a„d Silurian System Since a* 
” W °t7* ‘'"“''‘f' * T "" '»»'• ”* noticed in i« have been discovered. Thus, i„ 
c, „o p r rr ff hor “■* « it. tm — , .... 
Cnnorde. melndmg the remarkable bodies named Pseudoerinite. by Mr. C. Pearce, and which seem 
be allied to the genus Pentremite. 
