464 Trans. Acad. Sci. of St. Louis. 



correct, are strong indications of the lower Mississippian age 

 of the fauna, and offset the presence of such Devonian forms 

 as Ptydodus and Atrypa spinosa. In balancing these two 

 elements in the fauna, especial attention should be given to 

 the presence of the younger element, this being more signifi- 

 cent than the presence of the forms which are hold-overs from 

 an earlier fauna, especially since these hold-over forms are so 

 much modified as to be specifically distinct from their earlier 

 representatives in almost every instance. 



The true time relations of the Glen Park fauna are best 

 shown by making comparison with a similar fauna from an 

 oolite bed at Hamburg, Calhoun County, Illinois, which is the 

 only fauna so far known containing any considerable number 

 of Glen Park species. The lowermost Mississippian beds at 

 Hamburg lie unconformably upon a formation bearing a mid- 

 dle Devonian fauna of the lowan type, and two sections 

 through the beds at that locality clearly show the strati- 

 graphic relations of the faunas of Kinderhook age. Section 

 A is along the creek at the south edge of the village of Ham- 

 burg, starting from the bridge and running up the creek. 

 Section B is along the bank of the Mississippi river from the 

 mouth of the creek just south of the village to a point about 

 one mile north. These two sections will be described in 

 parallel columns, beginning with the lowermost beds.* 



SECTION A. SECTION B. 



1. Massive light colored lime- 1- Massive light colored lime- 

 stone with a few inches of clay stone as in section A. 



shale near the base. Fossils not 

 abundant, mostly a species of 

 Atrypa. 



Thickness, 18 feet. 



2. Arenaceous shaly flags pass- 

 ing into limestone above, with a 

 middle Devonian fauna of lowan 

 type. 



Thickness, 3-4 feet. 



2. Same as in section A. 



* These sections were made by Mr. R. S. Bassler of the United States 

 National Museum, and have been generously furnished to the writer by Mr. 

 E. O. Ulrich of the United States Geological Survey. The writer is also 

 indebted to Mr, Ulrich for the o pportunity of studying the fauna of these 

 Hamburg oolites. 



