26 THE DEVONIAN OF MISSOURI. 



and Callaway in most places. He also included the Sylamore 

 with the Devonian and called it "The old Red Sandstone." 

 (The Sylamore is the basal formation of the Mississippian.) 



Lithology. — The Callaway limestone presents various rather 

 strongly contrasted phases but is much the same lithologically 

 from place to place. Its thickest parts consist of light to dark 

 blue compact fine-grained limestone, in many places highly 

 fossiliferous. The limestone is relatively free from impurities. 



A light to dark-brown compact limestone is usually present 

 in from one to three or four thin beds, with a total thickness 

 in most places of less than 6 feet. Some of these beds are highly 

 fossiliferous. 



A third phase of the Callaway consists of white to gray 

 coarsely to finely crystalline limestone, in many places highly 

 fossiliferous. The crystalline phase occurs in one to three or 

 four lentils and the lentils range from 6 inches to three or four 

 feet thick. 



At many places a sandstone, ranging up to ten feet thick, 

 and often highly cross-bedded, occurs at the bottom of the forma- 

 tion. The bottom limestones, where the sandstone is absent, 

 are often sandy, and sandstone lenses are not uncommon near 

 the bottom. In eastern Moniteau County more than twenty 

 feet of cross-bedded sandstone makes up most of the forma- 

 tion. 



Much of the Callaway is highly fossiliferous and the entire 

 rock in some places is composed of fossils. One thousand speci- 

 mens of Atrypa reticularis (Linnaeus) were counted in ten pounds 

 of average weathered material. 



The maximum thickness of the Callaway is about fifty 

 feet and it averages 30 to 40 feet through Callaway and Mont- 

 gomery counties. It is very irregular in thickness, owing to its 

 having been deposited on an eroded surface and its upper surface 

 having been deeply eroded in pre-Mississippian time. It is 

 absent in many places short distances from where it is best 

 developed. 



Exposures in Moniteau County. — The westernmost outcrops 

 of the Callaway are in the bluffs of the Missouri River near 

 Lupus in Moniteau County, and it dips under northward about 

 two miles north of Lupus. Westward it dips under, but its 

 horizon reappears a few miles west with no Callaway present. 



The most striking feature of the formation in Moniteau 

 County is a thick sandstone that resembles the St. Peter. This 



