548 IOWA ACADEMY OF SCIENCE Vol. XXV, 1918 



lost sig-ht of. Paleogeographical relations are forgotten. Pal- 

 eontologie evidences are not analyzed. Litliologic similarities 

 are overlooked. Similarity of lithologic sequence is passed over 

 as if of inconsequential character. Fundamental canons of cor- 

 relation are completely ignored. 



Another important feature directly bearing upon the con- 

 sanguinity of the Illinois or Eastern Interior with the Western 

 Interior field is the recent determination of the eastward ex- 

 tension of the Bethany limestone or basal member of the Upper 

 coal measures far beyond its previously recorded limits. This 

 discovery in the trough of the great Cap-au-Gres fault in north- 

 central Missouri places the boundary of that member more than 

 50 miles in advance of any hitherto recognized eastern outcrop, 

 and within only 50 miles of the Illinois line. 



There are several advantages in selecting for the Illinois area 

 the coal measures section constructed by A. H Worthen. This 

 section is made up in the same way as was the eastern Kansas 

 section. It was erected under the guidance of F. B. ]\Ieek, who 

 was at the time a co-laborer of Worthen and than whom no 

 worker was more familiar wdth the Kansa-s sequence. Worthen 's 

 section has a further advantage over later ones in that it goes 

 into sufficient detail and was made by one who had gone over 

 the whole field. 



Adjudicating the paleogeographical affinities of the Illinois 

 coal measures according to the standard of the Kansas, Missouri 

 and Iowa sections there appeal's to be in the several successions a 

 wonderfully close correspondence in general features. This 

 parallelism is well indicated in the subjoined table : 



