SILURIAN FAUNA INTERPRETED EPICONTINENTALLY 70! 
Europe, and their entire absence from New York where the 
fauna has really been more carefully studied than in any other 
part of America, is, to say the least, suggestive. If there had 
been a direct east and west pathway of communication between 
Europe and the interior of North America, why have not some 
of these forms also been found in New York, an intermediate 
locality which would have been in the direct path ? 
Only a few of the more remarkable forms common to the 
Mississippi valley and northern Europe, but absent from New 
York, have been mentioned. There are many others in various 
classes, of a more modest and ordinary appearance, which need 
not be specifically mentioned here. The trilobites of the 
Chicago fauna, however, when properly studied, bid fair to bring 
out fully as remarkable points of relationship between the two 
faunas as the forms already mentioned. 
The facts of the distribution of the life indicate clearly that 
northern Europe was more closely associated with the Missis- 
sippi valley than with the New York region in Silurian time. 
The sea-shelf connection must have been in either a southern, 
western, or northern direction from the interior of America. If 
it is shown that the Appalachian land extended westward across 
the southern part of the United States in Silurian time, the 
southern route is barred, but if that land was not present the 
pathway of intermigration would have been around the southern 
end of Appalachia and then north along its eastern shore and 
across to Europe. According to the mode of interpretation here 
adopted, it should have been, under these circumstances, along 
the sea-shelf of the north Atlantic, except as the species were 
adapted to pelagic migration, and as the Silurian strata in the 
eastern provinces of Canada lie in this path, some of the peculiar 
forms mentioned might be looked for in their fauna, but they are 
entirely absent so far as known. However, the stratigraphic 
evidence seems to shut off this southern route, because the 
Silurian strata grow thin in that direction and become more 
clastic, exhibiting every evidence of having been deposited near 
a shore line. 
