An Account of the Middle Silurian Rocks of Ohio and Indiana. 



191 



When it is attempted to correlate the Indiana with the Ohio 

 section, it is found that the Belfast bed in Indiana shows all the char- 

 acteristics of the Belfast bed in its exposures west of the eastern and 

 more typical line of outcrops in Ohio. 



The Clinton of Indiana, though often much thinner than the 

 Clinton of Ohio can easily be recognized and distinguished as a 

 separate formation from the rocks above and below. 



The typical Laurel bed' is recognized as a mass of well bedded 

 white or bluish-white limestone, easily quarried as nagging stones, 

 which at New Point and to a less degree, at Osgood, shows few inter- 

 calated chert beds, but which near Laurel and Longwood contains a 

 considerable number of these chert beds intercalated between the 

 upper half of the limestone layers. North of Osgood the basal portion 

 of this Laurel limestone formation is richly fossiliferous and this 

 portion might hence be appropriately called the Osgood phase of the 

 Laurel formation. It will not do however to imagine that it could be 

 distinguished from the rest of the Laurel formation as a separate bed, 

 since the two species, Pisocrinus gemmiformis, and Stephanocrinus 

 osgoodensis, which characterize it, are also found in the upper part of 

 the formation at the quarry south-west of town. A great part of the 

 remaining species occur in the Waldron shales, which belongs, im- 

 mediately above the Laurel formation. The Laurel formation can be 

 readily identified 2 miles north of Fair Haven and at the west end of 

 New Paris, where the corresponding rocks include even chert layers 

 interbedded so characteristically in the upper part of the Laurel form- 

 ation at Laurel. The Laurel formation can also be readily identified 

 north-west of Euphemia, and at James Carl's quarry, 3^ miles south- 

 west of Lewisburgh, although the intercalations of chert in the upper 

 beds at these localities are absent. At the latter locality the upper 

 part of the formation even contains Pisocrinus gemmiformis and 

 Stephanocrinus osgoodensis, as in this formation at Osgood. A close 

 examination of the rock north-west of Euphemia suggests that it is 

 not impossible that' the upper half of the formation, above the clayey 

 and shaly layers, represents the so-called " Niagara shale" of more 

 eastern region. Going to the exposures at Ludlow Falls, this sug- 

 gestion is strengthened since here the Dayton stone is seen to merge 

 gradually upward into a more magnesian and at least softer and more 

 drab colored or brownish rock, such as is called the " Niagara shale" 

 in Montgomerycounty and elsewhere, when more readily distinguished 



