Keol-'il- GroHj), Mississippi Valley. — Beachhr. 91 
stone,* attaining in Montgomery count}', Indiana, a maximum 
thickness of about tiiree hundred and fifty feet. In eastern Ken- 
tucky the rocks occur in the tops of the knobs resting upon the 
knobstone. in western part of state they thicken up reaching their 
maximum thickness in Hardin and southern part of Barren 
counties. Tennessee and Alabama the rocks assume a silicious 
character and are known as tlie Silicious group, attaining a max- 
imum thickness of not less than five hundred feet. 
a. The Chn-ty n,<L 
succeeds the Upper Burlington limestone and appears on the 
Iowa side at the -'Cascade" south of the city of Burlington, 
where the extensive quarrj'ing has developed a great number of 
fine transition forms of crinoids. from which the bed receives the 
name of fnoisitioii led by paleontologists; the bed consists of 
thin alternating layers of chert and encrinital limestone, and 
sometimes an intermixture of l)oth. These l)eds next appear in 
the river bed above Keokuk forming the "rapids of the Missis- 
sippi river" where they attain a thickness of sixty to seventy feet. 
In Illinois this Ijed is seen along Hyde's creek three miles to 
Warsaw, thence to Nauvoo forming the lower part of the bluffs 
at Sagetown. In Indiana the only equivalent of the bed is found 
in eastern part of Montgomery county at New Ross where it loses 
its cherty character, the following section was observed: 
Soil 10 to 20 feet 
Argillaceous sandstone 3 " 
C'riaoidal limesloue 3 to 9 " 
Blue argillaceous liniestotie .... 2 to 4 " 
Blue shale 10 to - " 
In eastern Kentucky, geologists generall}' fipply the name 
•Keokuk"' to the shales and overlying knobstone, which rest upon 
the Genesee shales, and hold that the knobstone (Waverly) and 
Burlington groups are absent. At • -Button Mole knob"" in Bul- 
litt county as well as in the knobs at the edge of the city of 
Lebanon. Marion county, the knobstone. which Owen pointed out 
so plainly in Indiana, is well developed, with the equivalent of 
the Iowa cherty bed with its characteristic brachiopods. resting 
on top. 
*Ohio and Kentucky authors use the Ohio term Waverly; according to 
the 1 iw of oriority the name "Knobstone" has precedence as it was ap- 
plied b_y Owen iu 18oS in liis report of the Geological reconnassiance of 
Indiana made to the Legislature during that year. 
