±1± R. M. Field — Middle Ordovician of Central 



brought out after considering the conditions under which 

 the superjacent formations were laid down. 



The Carlim is closed with a zone (E') of shaly, impure 

 limestone, which is well shown in the foot-walls of all 

 the quarries. This zone is somewhat variable in thick- 

 ness and has been traced from Salona to Tyrone, a dis- 

 tance of over 90 miles. It contains a regular mat of 

 Tet radium fibratum and Beatricea gracilis? The upper 

 layer which forms the parting plane between the Carlim 

 and the Valentine was particularly well exposed in the 

 Belief onte quarries in 1917, where approximately one- 

 quarter of an acre of ripple-marked and mud-cracked 

 limestone was displayed on the steep foot-wall of the 

 largest quarry. 



Valentine Formation. — I have named the pure quarry- 

 rock, which follows the Carlim, from a small hamlet and 

 forge near Belief onte which are not shown on the county 

 map. The Valentine family was prominent in the early 

 mining industry of central Pennsylvania, and it seems 

 fitting that this valuable bed of limestone should receive 

 its name. 



Collie makes no distinction between the pure quarry- 

 rock and the overlying fossiliferous formations, all of 

 which he has grouped under the rather indefinite term 

 of "Black River." 



The Valentine does not occur in the section at Roaring 

 Spring, although Butts intimates that this section is 

 identical with those on the Tyrone-Salona line. The 

 contact of this unfossiliferous formation with the under- 

 lying Tetradia and Beatricea beds is sharp and clean-cut, 

 but its upper beds merge almost imperceptibly into the 

 superjacent Center Hall. The field relationships of the 

 Valentine will be discussed more fully after the descrip- 

 tions of the Center Hall. It is simply stated here that 

 this formation occurs as a lens in the upper Stones River 

 beds and is gradually replaced by them to the east. 



An examination of the thin section of the Valentine 

 limestone shows that the ground-mass is made up of 

 minute crystals and granular particles of calcium car- 

 bonate, which are barely distinguishable under a mag- 

 nification of 380 diameters. There is no evidence of 

 stratification except under high powers. Throughout the 

 ground-mass are scattered larger grains of calcite, some 

 of which are large enough to be seen macroscopically. 



A few scattered particles of the tests of trilobites are 



