702 STUART WELLER 
The western route need not be considered, because the Silu- 
rian fauna is not known to have any notable development in that 
direction. This leaves only the northern route. The presence 
in the Arctic localities of some of the peculiar genera already 
mentioned, would furnish the most substantial evidence in favor 
of this route. The conditions under which fossils have been 
collected in the Arctic regions have been such, however, that the 
fossil faunas of the far north are but poorly known. Although 
this is the fact, the genus Cvotalocrinus has been identified from 
a small island in Wellington channel* from specimens of the 
stem alone. The stem of this genus, however, is quite distinc- 
tive, and the identification is probably correct. The other forms 
mentioned have not yet been found there, but they probably will 
be if the proper opportunity for the study of those faunas is 
ever offered. 
If the interpretation here offered be the correct one, then the 
usual conception of the Silurian geography of North America 
must be somewhat altered. We must conceive of a North Polar 
sea with a great tongue stretching southward through Hud- 
son Bay to about latitude 33°. There were doubtless islands 
standing above sea level within this great epicontinental sea, and 
at the latitude of New York there was a bay reaching to the 
eastward in which the Silurian sediments of the New York 
system were deposited. There may also have been a secondary 
tongue reaching southwestward from some point in Canada, into 
the Rocky Mountain region. Labrador, Greenland, and Scan- 
dinavia were in a measure joined into one great land area, though 
perhaps with its continuity broken, with a sea-shelf lying to the 
north of it and another to the south. Another epicontinental 
tongue of this northern sea extended south into Europe, bend- 
ing to the west around the southern part of the Scandinavian 
land and connecting with a Silurian Atlantic Ocean. The sea- 
shelf to the north of the Labrador-Scandinavian land was a 
means of intercommunication between northern Europe and 
the interior of North America, and the sea-shelf to the south 
* Quart. Jour. Geol. Soc. Lond., Vol. IX, p. 315 (1853). 
