74 
BULLETIN OF THE LABORATORIES 
agara cap is here unfossiliferous as far as known. The Dayton lime- 
stone contains corals and orthocerites. Between the Clinton strata 
and the Dayton limestone is a bed of blue marl, 9 in. thick, which is 
referred to the Clinton Group. It contains large crinoid beads, 
Orthis biforata^ var. lynx, and various minute forms not known else- 
where in the series. The Clinton Group proper has furnished a py- 
gydium referred, doubtfully perhaps, to IllcEnus Madisonianus . The 
marl is in this paper called Beavertown marl. 
CENTREVILLE QUARRIES. 
Centreville, eight miles south of Dayton, is situated on an outlier 
of stone, composed of rocks belonging to the Clinton and Niagara 
groups. In some places that division of the Niagara Group known 
as the Dayton limestone or “ marble” approaches within a few feet of 
the surface of the ground, and hence gives rare opportunities for good 
and readily worked quarries. 
Alienas Qiiariy. 
Several years ago, shortly after the construction of the Cincinnati 
Northern railroad, a quarry was opened on the farm of John E. Allen, 
about a half a mile east of Centreville, ^ This quarry is probably the 
most easily worked and most accessible (for purposes of transportation) 
in the county. The Clinton rock is here of a pinkish or often dirty 
white color. It is exposed only by the removal of the overlying Ni- 
agara stone, or by the cutting of ditches. Yet many and often rare 
fossils have been found here. Orthis Daytonensis, with both valves 
preserved, has been discovered. A thin seam of bluish clay, be- 
tween the Clinton and Niagara stone, furnished the large Calymene, to 
be described later. This clayey layer has not yet shown any of the 
curious little fossils found in the marl at Huffman’s Quarry, although 
apparently its stratigraphical equivalent. 
Beginning with the base of the Niagara exposure, the courses of 
Dayton stone run as follows: a 16, i8j^, 6, 3j4, 2^‘, 4, 4^, 
and a in. course. Comparing these courses with those at Huff- 
man’s Quarry, it will be noticed that the 16 in. course corresponds to 
the 20 in. course of that quarry, and like it is divided into smaller 
layers : in this case into a 4 in. layer below and a i ^ in. layer above, the 
intermediate divisions, if any, not having been noted. The 18 j 4 in* 
and 6 in. layers also correspond very nicely to the equivalent divisions 
