514 GEOLOGY OF OHIO. 
thoceras, Plewrotomaria, and Syringopora. The stratum exposed here, I 
think, is the same as No. 4, at Gard’s quarries. 
Another exposure on the land of A. Dickey, near Weaver’s Station, 
south-east quarter, section 29, Neave township, shows only the surface of 
_ the Niagara limestone, it forming the bed of Mud Creek for 150 yards or 
more. So near as can be judged, the rocks here, as elsewhere, are hori- 
zontal, but differ slightly from the three exposures above.in other respects. 
They are distinctly laminated, breaking out in thin but irregular flags ; 
very sandy in texture, and mostly of the ordinary buff color, but in 
patches here and there have all the appearance of a red sandstone. The 
light colored portions, I understand from a very imperfect experiment 
performed there some years ago, produce a fine white quality of lime, but 
the other resembling red sandstone becomes very hard when subject to 
heat. This fact, I think, is attributable to imperfect burning. This rock 
was employed in the foundation of a mill which stands near by, but it is 
evidently too soft for building purposes. The utter absence of fossils or 
traces of any, is to be noted as a very peculiar feature compared with the 
Guelph beds in other portions of the county. 
The only other exposure of the Guelph rocks occurs on the lands of 
C. C. Walker, near New Madison, north-west quarter, section 24, Harrison 
township, where it was formerly quarried and burned for lime by C. B. 
Northrop, but has now been abandoned. -A much worn section of six or 
eight feet is still visible, showing the same general features of this 
formation as displayed elsewhere. 
It is impossible, from the meagre sections afonded: to give the exact 
measure of the thickness of this formation in Darke county. Prof. Orton 
gives to this phase of the Niagara rock at Hillsboro, Ohio, twenty feet, 
and at Springfield, where it prebably reaches its maximum, forty-two 
feet. Twenty or thirty feet, however, might be considered a safe esti- 
mate here. , 
The fossil contents constitute a far more interesting feature of the 
Guelph beds than any yet described. The life here indicates somewhat 
different conditions from those shown by the division elsewhere. 
First might be noticed the rarity of Pentamerus oblongus, but four or five 
specimens having ever been found. Its place, however, as to abundance 
and otherwise, is fully supplied by another species of the same genera, 
P. pergibbosus. Lower down in this formation, both at Covington, Miami 
county, and New Paris, Preble county, the P. oblongus constitutes a good 
part of the rock. All fossils here, it must be remembered, are repre- 
sented by casts; and ‘though the rock weathers very rapidly, the casts, 
when newly exposed, are for the most part very beautiful and perfect. 
