Foerste.] 
350 
[May 1, 
of these forms in the Clinton. The first is that the fossils in question 
favored certain localities in the sea possibly those nearer the shore, 
and that these shore conditions did not occur at the anticlinal until 
at a later period. The extreme variability of shore conditions how- 
ever implied by the character of the rocks farther eastward and 
the probability that parts of the anticlinal showed more shore ac- 
tion during the Clinton than did at least Anticosti, leaves, however, 
scarcely any margin for such a supposition. 
The second is that the species in question may have been mi- 
grating towards the west at the time in question after the close of 
the break of the paleontological record, between the Upper and Lower 
Silurian epochs, and that the} 7 did not reach the anticlinal until 
after the close of the Clinton period of that region. If this could 
be established by further observations it would be an interesting 
point in paleontological research. But if they migrated, where did 
the forms come from originally? As far as may be determined from 
the character and thickness of the rock deposits now remaining 
from that time, the land of the Clinton sea seems to have been 
nearest southeastern Pennsylvania, and thence to have curved 
around towards the Atlantic, both on the north and the south, per- 
haps more rapidly towards the north. This land, judging from 
the contributions it made to sedimentary strata, from the Clinton 
to the upper Carboniferous periods must have had decidedly conti- 
nental proportions. To our knowledge the sea deposits along the 
northwest of this paleozoic continent at present represented in 
part at least by the deposits of Anticosti was the only place show- 
ing comparatively no paleontological break between the Lower 
Silurian and the Clinton rocks and very likely was one of the 
sources from which certain of the Clinton fossils of the anticlinal 
came. The distribution of such forms as Pleurotomaria var. occi- 
dens, Holopeci obsoleta var. elevata and Spirifera rostellum, make it 
probable that such continuous breeding places for species existed 
also along the southwestern side of the paleozoic continent. 
No doubt intermediate localities occurred of which we have no 
record and the position of which we cannot at present reconstruct. 
The very great range of many of the Clinton fossils, from Anticosti 
and New York to Alabama, while at a short distance off the line 
toward the westward they are absent for a time, or even perma- 
nently, make it probable that the species migrated north and south, 
comparatively freely in the shallower waters off the shore of the 
paleozoic continent, but that they found some physical obstacle in 
