284 STUART WELLER 



made that it has not been possible to adapt any part of the scheme 

 to the more recent work on the series. In the first place the 

 Ste. Genevieve limestone was mistakenly included in the Chester 

 Group because of the failure to recognize that the upper member 

 of this Hmestone as defined, the Ohara, was really made up of two 

 very distinct parts, only the upper one of which is really Chester, 

 and this "Upper Ohara" really has no place whatsoever in the 

 Ste. Genevieve limestone when that formation is properly Hrnited 

 in accordance with its typical exposures in Ste. Genevieve County, 

 Missouri. In the second place the sandstone designated as Cypress 

 by Ulrich was not the Cypress of Engelmann, but the bed that was 

 properly sandstone No. 10 of that author. In the third place, beds 

 which really belong in three totally different positions in the Chester 

 series were designated as Tribune limestone. The limestone at 

 Tribune, Kentucky, which gave origin to the name, has more 

 recently been shown to occupy a position far above that designated 

 for the formation, and is in fact representative of a limestone 

 member far up in the Birdsville formation as defined by Ulrich. 

 At another locality the so-called Tribune is a limestone beneath 

 the sandstone that was mistakenly called Cypress, while elsewhere 

 it does occupy the position assigned to it in the definition of the 

 formation, above the miscalled Cypress sandstone. In the fourth 

 place the Birdsville formation of Ulrich comprises a succession of 

 limestones, sandstones, and shales, and is as lacking in utility as 

 a formation as was the older name, Chester formation. 



The work upon which the present paper has been based has 

 been carried on continuously under the auspices of the Illinois 

 State Geological Survey, from 191 1 to the present time, and was 

 preceded by more general observations upon the Chester series 

 since 1906. From 191 1 to the present time the work of mapping 

 in detail the Chester series in Illinois has been in progress, and it 

 has now covered the counties of St. Clair, Monroe, Randolph, 

 Jackson, Johnson, Pope, and Hardin. The only portion of the 

 Chester belt across the state that has not been studied and mapped 

 in detail at the present time is in Union County and a corner of 

 Jackson, and reconnaissance observations in Union County have 



