1890.] St. Louis Limestone. 311 
Kentucky, Tennessee, and Alabama. “This fossil is one of the 
most widely distributed corals of the Carboniferous limestones, 
and appears to hold the same geological position from Central 
Iowa to Alabama, everywhere marking the horizon of the St. 
Louis limestone.” © In Iowa both the fossiliferous and unfossil- 
iferons kinds of rock may be observed in the regions of the 
brecciated limestone. In some cases masses of the coral are 
found unbroken, but usually they are in a fragmental condition. 
In the vicinity of Keokuk we have observed places at which the 
limestone pieces are conspicuously fossiliferous, abounding in 
broken fragments of the above coral, as well as other fossils in a 
more or less comminuted condition. On the whole, however, 
the brecciated portions are comparatively unproductive of fossils. 
It is significant that n its extension northeastward into Ohio and 
Pennsylvania no remains of ZL. canadense are found, though 
Meek has shown this formation to be present in that region. 
2. The character of the St. Louis towards the south corre- 
sponds with what might be expected in its more seaward portions 
It there becomes more evenly stratified and greatly more fossil- 
iferous. The brecciated character is nearly lost, appears only at 
intervals, beginning and ending abruptly, and the intermediate 
portions showing more or less oblique laminations. 
4. The uneven surface of the brecciated limestone would be a 
Necessary sequence of the development of land seaward along a 
reef-bound coast. ' : 
On the retreat of the sea the lagoons and intermediate spaces 
were filled by shore-wash, accompanied by a luxuriant E 
and land progression outward, similar to that of Florida, TO 
by Agassiz, in more recent times. Under this hypothesis the 
irregular pockets and basins of coal in the Lower es m 
are easily accounted for. They result from the accumulation 
within the lagoon of vegetation growing upon a _— as 
transported from without. That in these cases it did not in 
Mame act that the coal rests 
cases grow in situ would appear from the fact è i 
almost immediately upon the limestone with po intervening T 
to form a soil for its growth. In other localities the coal is un 
10 Hall, Geology Iowa, Vol. I., Part I1., p. 668. 
