296 C. H. Gordon — Keokuk Beds at Keokuk. 



12. Soft, gi'itty shale, readily decomposing on exposure to 

 atmospheric influences. Filled with geodes varying in 

 size lrom one to four inches in diameter. Thickness.. 15 ft. 



11. Shales, more calcareous, with occasional bands of lime- 

 stone. Geodes fewer but larger. Thickness .20 ft. 



10. Limestone, hard, in thin variable layers. Thickness 2 ft. 



9. Dark blue argillaceous shale. Contains no geodes. 



Thickness 2 f t. 



I. Calcareous Division. 



8. Limestone, light gray, changing to light brown or yellow 

 on exposure. Crinoid bed No. 2, sometimes called the 

 Dorycrinus bed. Batocrinus Nashvillce Troost, B. 

 biturbinatus Hall, Dorycrinus 3fississi2ip>iensis Roemer, 

 Agaricocrinus Wortheni Hall. A. Americanus, var. 



? Barryerinus tumidus Hall, Archimedes Oweni- 



ana Hall, etc. Thickness .1 to 2 ft. 



Lenticular layers, prolific in crinoids, are sometimes found in- 

 tercalated between 1 and 8. 



1. Hard blue limestone; layers thin. Thickness, . 3 to 5 ft. 



6. Heavy dark blue limestone with nodules of chert. Fish 



bed No. 2. Thickness 2 to 4 ft. 



5. Blue subcrystalline limestone in layers 6 to 12 inches 

 thick, alternating with similar layers of shales. Single 

 valves and casts of Spirifer Keokuk Hall, abundant. 



Thickness 8 to 15 ft. 



4. White or light gray massive limestone called White 



Ledge by the quarrymen. Fish bed No. 1. Thickness. 4 ft. 

 At this point the partings frequently contain crinoids, while in 

 some places a thin crinoidal layer is iound resting upon the roll- 

 ing cherty surface of the layer below. Actinocrinus, Agarico- 

 crinus Americanus Roemer, Barycrinus magister Hall, etc. 

 3. Impure shaly limestone with occasional bands of chert. 

 Contains pockets of calcite in large beautiful crystals. 

 Thickness 6 ft. 



2. Light gray comparatively soft limestone. Crinoid bed 



No.l. Species numerous. Agaricocrinus Americanus 

 Roemer, also two varieties. Actinocrinus pernodosus 

 Hall, A. Dowei Hall, Batocrinus lagunculus Hall, 



Platycrinus Saffordi. Thickness 6 in. to 1 ft. 



1. Massive blue or drab subcrystalline limestone. Occa- 

 sional specimens of fish teeth belonging to the genus 



Chitonodus. Thickness . >3 ft. 



The parting between this and the beds below filled with stems 

 and joints of Eucladocriniis. 



Transition Beds. 



Limestone in thin layers; cherty. Thickness exposed 6 ft. 

 Platyceras fissurella Hall, P. equilatera Hall, Palmcis obtusus M. 

 and W., Batocrinus planodiscus H., etc. 



