448 G. R. Keyes — Fauna at the Base of the 



At Louisiana, in Pike County, Missouri, which is separated 

 from Pike County, Illinois, only by the Mississippi River, the 

 " white chert " beds are much better developed than any 

 where else in the region. It is from the Missouri locality that 

 the recent collections have been made. Here the Burlington 

 limestone is well exposed in the hilltops, where extensive 

 quarries have been opened. 



For more than 70 miles, from above Quincy to below 

 Louisiana, the Burlington limestone forms an almost contin- 

 uous mural escarpment capping the high bluffs on either side 

 of the Mississippi River. These bluffs rise to a height of 

 from 300 to 400 feet above the water level. In many places 

 they form bold, overhanging cliffs, with a heavy talus at the 

 base. 



A vertical section of the rocks at Louisiana is as follows : 



Feet. 

 16. Brown and white, compact, encrinital limestone, 



thinly bedded, with some chert . . - . 75 



15. White, encrinital limestone, very heavily bedded, 12 

 14. Coarse-grained, encrinital limestone, with irregu- 

 lar chert bands . 20 



13. Very heavily bedded, white encrinital limestone, 

 with a peculiar white chert in nodules and 



irregular bands 11 



12. Brown, encrinital limestone, compact and heavily 



bedded, somewhat earthy in places 15 



11. Compact, fine-grained, bufF limestone, with few 



or no partings 15 



10. Sandy shales, brownish, forming soft, friable 



sandstone locally - 12 



9. Greenish, clayey shales 70 



8. Thin-bedded, compact limestone, fine-grained, 

 with coochoidal fracture, in layers 4 to 6 inches 

 in thickness, like lithographic stone in texture 



and appearance , _ . 50 



7. Sandy clay-shale 3 inches. 



6. Drab or greenish clayey shale. 2 



5. Black, fissile clay-shale 4 



4. Buff, magnesian limestone, very heavily bedded. 10 



3. Compact, white oolite 5 



2. Blue clay-shale, with thin bands of impure lime- 

 stone rich in fossils 60 



1. Heavily bedded limestone, exposed 5 



Number 1 is the Trenton limestone ; 2 the Hudson River 

 shales. 3 and 4 probably represent the Niagara limestone ; the 

 first increasing rapidly in thickness southward and in a dis- 

 tance of 20 miles reaches a vertical measurement of 30 to 40 



