266 liingueberg on the Uiagara Shales. 
observe how far this theory is supported by the facts of the 
case. 
The thickness of the shale in western New York and its 
thinning out in both directions, show that a depression then 
existed at this point.' That this depression was of comparatively 
rapid formation is shown by the following facts: The shale is 
deposited directly upon the unevenly drifted surface of the 
Transition limestone, as before noted.^ 
The upper surface is extremely irregular and undulating; having the 
appearance of being drifted together. This is also corroborated by the 
position of many of the fossils which seem to have been swept together 
by eddies, charged with sedimentary matter, by which they were en- 
tombed as we now find them. 
This w ould also account for the perfection of the contained fos- 
sils. The spots where no trace of the Transition is to be found, 
were probably in the direct line of currents that had sufficient force 
to clear the surface of any deposit which might have been made, 
and to hold in suspension whatever sedimentary matter they con- 
tained. Such currents would also pick up and carry along such 
animal life of this closing scene of the Clinton, free or readily de- 
tachable, that lay in their paths; and after their force was spent 
deposit the same indiscriminately with the mass of foreign mat- 
ter they had brought with them. There are no regular lines 
of stratification, as a rule, to be observed in this stratum. Whole 
groups of species disappeared almost as suddenly as they ap- 
peared; such as the Cyrtoceratidce.,wh.\c\\ are to be found abimd- 
antly in some localities in this formation, while immediately 
before and afterwards they are almost unknown. So it is with 
quite a number of species which are otherwise strangers in this 
vicinity. 
It is evident, however, that the changed condition of things 
was more in conformity with the physical surroundings to 
which the newcomers had been accustomed than that existent 
during the latter part of the Clinton, for we find a greater pre- 
ponderance of survivals among the transplanted forms than 
among the original inhabitants of the region. 
With such a birth we can well expect an interesting period 
' Prof. J. Hall. 28th Regents Rept. on the N. T. State Museum^ p. 102. 
' Amer. Nat. ib. 
