814 E. O. ULRICH CORRELATIONS OF CHESTER FORMATIONS 



fewer characters — can not have been evolved either before or after the 

 particular time in geologic history in which it existed. In other words, 

 no such combination of major and minor features can have occurred 

 more than once; hence I maintain that the occurrence in two or more 

 places of accurately identified specimens of species or varieties that are 

 alike in all details of structure affords the most reliable known means of 

 establishing the contemporaneity of the beds from which the fossils were 

 taken. 



Of course, like any other means of correlating geologic formations, 

 this principle must be applied with discretion and all due regard to 

 differences marking stages of growth and to those that are to be counted 

 as strictly individual. 



AVeller treats me ungenerously and with actual unfairness in his dis- 

 cussion and frequent reiteration of the fact that in 1905 I applied the 

 name Cypress to a sandstone formation that is older than the one at the 

 type locality of the Cypress. Nobody then knew — nor did any one, in- 

 cluding Professor Weller, suspect before 1915, when Butts, after joining 

 Weller in the study and areal mapping of the formations in southeastern 

 Illinois, discovered the facts in the case — that the true Cypress on reach- 

 ing the Ohio at Golconda dropped in the section almost into contact with 

 another older sandstone, the two together making the bluff along the 

 river through most of the distance between Golconda and the Hardin 

 County line. Neither did Weller nor any other geologist know before 

 Butts' discovery of the tripartite character of the sandstone bluff that 

 the sandstone in Downeys Bluff at Rosiclare, which had been mapped by 

 Worthen and Engelmann as the Cypress sandstone and which was my 

 type of the sandstone that I mapped under this name in Kentucky, is in 

 fact only the lower of the two sandstones occurring in the bluffs both 

 above and below the town of Golconda. 



The misnaming of the Tribune limestone and my erroneous correla- 

 tion of this limestone with the subsequently named Okaw limestone of 

 the section in western Illinois was admitted and explained in the Ken- 

 tucky Survey volume. Besides, the name Tribune has been dropped and 

 the Gasper limestone, by which name the formation described by me in 

 1905 under the discarded term is now generally known and accepted, is 

 fully described and clearly defined by both Butts and myself in the Ken- 

 tucky work. Surely this kind of "rubbing it in," including a quotation 

 (page 128) from a letter written by me in 1911, can serve no good pur- 

 pose. It would have been more generous and better all around to have 

 ignored and forgotten such relatively trivial lapses. The only thing 

 worth remembering about the Tribune limestone is that under this name 



