Age of .the Cincinnati Anticlinal. — Foerste. '■»!• 
They resemble therefore the limestone pebbles of many less im- 
petuous fresh water streams where abrasion plays a less important 
part, owing to the small velocity of the current. Such an origin 
cannot, however, be predicated of them. Their presence is cer- 
tainly suggestive of shallow water condition over this part of the 
Cincinnati anticlinal region during the Clinton period. 
Recent examination of Clinton oolitic iron ores has shown that 
in many places most of the so-called oolitic grains are the rounded 
fragments of small bryozoa, more or less replaced by iron ore. 
Sometimes the original bryozoan structure is not much altered and 
only the cell spaces are filled with iron ore. which also in this case 
probably represents original calcite material, that part which had 
penetrated into and filled the cells of the original bryozoan struc- 
tures. Grains may be found where both the calcite of the 
bryozoan grains and their cell filling are unaltered; where the 
calcite of the bryozoa has been more or less replaced by iron ore, 
and is in marked contrast with the unaltered calcite cell-filling; 
where the calcite of the bryozoa is but little altered and that fill- 
ing the cells is more or less replaced by iron ore; finally, where 
the calcite both of the bryozoa and that filling their cells are re- 
placed by iron ore. In the last case the replacement may be so 
complete that the original bryozoan structure can no longer be 
detected. It will be remembered that in speaking of the Belfast 
conglomerate, pebbles were said to decrease in size until the 
smallest were only of the size of small grains. It is likely that 
some of these so-called oolitic grains, in which no structure can 
be detected, represent such fragments of older limestones, not oi 
immediate organic nature, now replaced by ii-on. The general 
cement enclosing the grains is sometimes replaced by iron ore, 
while part of the included grains are still unaltered; reversed con- 
ditions are also frequent. These bryozoan remains were detected 
abundantly in the Clinton oolitic iron ores of the Alleghanies. 
They were examined only at one locality in the neighborhood of 
the Cincinnati anticlinal — the upper courses of the Clinton 
group along Todd's Fork, north of Wilmington, Ohio. 
The presence of these small rounded bryozoan Fragments is cer- 
tainly indicative of the contemporaneous existence of currents. 
Such currents, however, might have been active in the deeper sea-. 
and the existence of currents is therefore no indication of shallou 
