296 STUART WELLER 



counties, but the shales that are present commonly weather into 

 a red, residual clay which somewhat resembles the material 

 in the red bed of the Mississippi River section. When not 

 weathered, the Paint Creek shale of the southern counties is very 

 fissile, breaking into thin, brittle flakes which are slightly olive 

 green in color when dry, but appear quite black where the exposures 

 are in situations where the rocks are kept constantly wet. In one 

 locality in Johnson County a bed of somewhat variegated red and 

 blue shale has been observed similar in character to some of the 

 beds in Monroe County. 



The limestone layers included in the Paint Creek formation in 

 the southern counties vary greatly in character. In places some 

 of these layers are very siliceous, some of them being little more 

 than layers of sand firmly cemented with calcium carbonate, other 

 layers are hard, dense, and compact with few or no sand grains, 

 still other beds are quite free from silica, and some of them, at 

 least, are more or less coarsely crystalline, dark Hmestone, quite 

 like some of the beds in the more typical exposures of the forma- 

 tion in Monroe County. 



The fauna of the Paint Creek is uniform in its essential features, 

 through the full extent of the formation in Illinois. It has much in 

 common with the faunas of the Renault, and the two formations 

 together constitute the two fossiliferous horizons of the Lower 

 Chester. The bryozoan Cystodictya labiosa is common in both 

 horizons, as are the species of Talarocrinus with bilobed bases, but 

 the Paint Creek fauna includes a much greater number, both of 

 individuals and species, of Pentremites, and the bryozoan genus 

 Archimedes is far more abundant than in the Renault. The same 

 species of Pentremites are present in the fauna from St. Clair to 

 Hardin counties. 



The Paint Creek occupies the position in the section which was 

 originally assigned to the Tribune limestone by Ulrich, though it is 

 by no means the equivalent of the formation so named, at Tribune, 

 Kentucky. More recently Butts^ has proposed to substitute the 

 name Gasper for Tribune, because of the unfortunate choice of 



' Butts, Mississippian Forinations of Western Kentucky (191 7), p. 64. 



