406 A. F. FOERSTE — LIMESTONES OF TENNESSEE AND KENTUCKY 



limestone are underlaid by 6 inches of soft limestone, 4 feet of harder 

 limestone, I2 feet of limestone weathering more readily, and 5 feet of 

 clayey limestone, also weathering readily. The base of the Osgood bed 

 is not exposed. These softer limestones occupy the same horizon as the 

 shaly Osgood cla3's at South Tunnel and Bledsoe. 



At the base of the cliff west of R. S. Elam's house, a mile above Fly's 

 store (locality 19), the Osgood bed consists of soft limestones, weathering 

 more readily than the Laurel limestone above. In fact, the Osgood bed 

 weathers so readily that it is difficult to find good exposures in the Leipers 

 Creek valle3\ At the Elam locality the Osgood limestone contains 

 a number of large specimens of Orthoceras. The presence of large speci- 

 mens of Orthoceras becomes rather characteristic of the Osgood limestone 

 along the valley of the Tennessee river, farther westward. Opposite the 

 home of C. E. Harris, on Snow creek (locality /f ), 2 miles east of Santa 

 Fe. only the harder layers of Osgood limestone are preserved. Their 

 identity is established by their position between the cherty layers form- 

 ing the upper half of the Clinton and the fairly well exposed base of the 

 Laurel limestone. Above Carol Litton's house the Osgood bed is absent. 

 At the Oil well below Tom Fox's home (locality 18) the 6 feet of lime- 

 stone beneath the Black shale and overlying the cherty Clinton belong 

 to the Osgood horizon. 



At Centerville, along the railroad (locality 25), the Laurel limestone, 

 25 feet thick, is underlaid by a somewhat softer limestone 4 feet thick, 

 weathering in some j)laces to a clayey calcareous rock. Beneath this is a 

 calcareous rock 6^ feet thick. In some places it is a rather firm limestone, 

 but it also occurs in the form of soft and shaly strata, readily weather- 

 ing, although strongly calcareous. As a matter of fact, the Osgood bed is 

 here lithologically sim})l3' a softer phase in the general Silurian section, 

 although paleontologically it separates the fauna of the Clinton limestone 

 below from that of the Laurel limestone above. 



At Montgomery's mill (locality 27), on Piny creek, the Osgood bed 

 forms likewise merely the softer phase at the base of the general lime- 

 stone section. 



It will be noticed from the })receding statements that the Osgood bed, 

 on being followed from its most northern outcrops in Tennessee south- 

 westward along the flank of the anticline, changes from a soft shaly clay, 

 easily distinguished from the limestones above and below, first to an in- 

 durated clay, especially near the top of the section, next to an even 

 harder calcareous rock, again chiefly at the top of the formation, and, 

 finally, at Linton and along the various tributaries of Duck river, it 

 becomes a soft limestone. Where the Osgood bed is represented by lime- 

 stone, its identity can be established only with difficulty. While, there- 



