Aln)ItlONAI. NOTES ON THE (^AMHRIAN OF CAFE HUETON. 
io5 
(B) The Tremadoc Fauna. 
In this fauna one enters upon the debatable ground between Cam- 
brian and Ordovician. In the Edition of Dana’s Geology, 1875, this 
group was classed as Silurian {i. e. Ordovician). In the later edition 
(1896) it is transferred to the Cambrian. Prof. Jas. Hall referred 
species of this fauna from the Sandstones of the Mississippi valley to 
the Potsdam (therefore Cambrian) in 1863 ? Director Walcott has 
referred strata in the west of America and at Saratoga, N. Y., hold- 
ing this fauna to the Potsdam or Upper Cambrian. 
But in Europe the consensus of opinion (omitting Great Britian) 
places this fauna in the Ordovician or Lower Silurian. Lindstruun 
says that in Sweden not one species passes from the Cambrian to the 
Ceratopyge Fauna (i. e. the Tremadoc) while nineteen species pass 
from the Ordovician to the Silurian (Upper). Four species, however, 
are recorded as passing in Wales from the Lingula Flags to the Tre- 
madoc Group.* Elsewhere it is stated that 6 out of 37 species of Crus- 
tacea pass from the Tremadoc to the Arenig in Wales.! So that it is 
difficult to draw a line of absolute division between Cambrian and 
Ordovician either above or below the Tremadoc. 
On the whole it seems better to hold to the prevalent English 
opinion which places the line of the division above the Tremadoc, not- 
withstanding the conditions that prevailed in Northern Europe, and 
notwithstanding the fact that new and important genera of crusta- 
ceans appeared in the Tremadoc slates. 
To adopt the line drawn by the paheontologists of Scandinavia and 
Germany would make necessary a revision of the Cambrian geology of 
America, whereby large areas and extensive faunas that have been 
classed as Cambrian would of necessity be transferred to the Ordo- 
vician, or Lower Silurian. 
Further, it may be inferred that this hiatus in the faunas will be 
bridged over by the discovery of connecting faunas in the strata of 
some other region than that of Europe. The Mount Stephen fauna, 
for instance, in British Columbia, associates genera of Ffestiniog, Dol- 
gelly and Arenig types, and generally in the Rocky Mountain region 
there is a blending of Cambrian and Ordovician types. For these reasons 
it seems undesirable to abandon the old classification which drew the 
*Mem. Geol. Surv. G. B., vol. iii, p. 8<!5, etc. 
I Ibid. p. 3.53. 
