-/^. Winchell on the Taconic Question. 355 
inferior to that of the series designated as Silurian by Murchison. 
But it subsequently appeared that the upper portion of them 
was the equivalent of strata in the continguous county of 
Shropshire, which Murchison had already annexed to his Silur- 
ian, under the designation of Lower Silurian — assuming that 
one sj^stemic designation could properly include a palcEontologic 
and stratigraphic break as abrupt as that between the "Upper" 
and " Lower " Silurian. The Cambrian of Sedgwick extended 
from the top of the Bala rocks to the bottom of the Llanberis. 
Their position was below the Silurian of Murchison as first con- 
ceived by himself, but was embraced in what may be called the 
Silurian annex. 
3. Strati grafhical relations of the Cambrian. Meanwhile, 
M. J. Barrande was at work on the geology of Bohemia. In 
1 85 1, appeared his publications in the Bulletin de la Societe ge- 
ologiqtie de France., and in 1852, the first volume of his Systeme 
silurien de la Boheme. In these was introduced his classifica- 
tion of older rocks into stages denoted by the letter A, B, C, 
etc., and the more important recognition of certain great palas- 
ontologic breaks, separating a succession of distinct systemic 
faunas, thus: 
E to H. Third fauna, 900 feet. 
D. Second fauna, 6,000 feet. 
C. Pi-imordial fauna, 1,200 feet. 
A and B. Azoic schists, 9,000 feet. 
When the same strict principles of palaeontologic classification 
came subsequently to be applied to the oldest rocks of Great 
Britain and America, the following conclusions were apparent: 
(i). The true primordial fauna had not been embraced in 
t)ie proposals of either Murchison or Sedgwick. The rocks 
containing this fauna in Bohemia extend "on an average, ten 
thousand two hundred feet" below any fossiliferous strata then 
known to Murchison or Sedgwick. Barrande embraced this 
entire extension under the name " Silui-ian," because he had 
then (1852) no knowledge of what had been done and projDosed 
by Sedgwick in 1836, or by Emmons in 1842. 
(2). The "sedimentary base" of the Taconic system signal- 
ized by Emmons in 1842, and synchronized with his "palaeozoic 
base," fixed in 1844, did reach down to the primordial fauna of 
Barrande, and included it. So that Emmons was guided by a 
