318 UMAR Tree LID NAIEGS) 
this shale bed grows rapidly in thickness, until at Keokuk it 
reaches 195 feet. 
The Louisiana limestone, which is over 50 feet thick at the 
type locality, appears to get thinner northward. At Keokuk it 
is only Io feet in thickness, and seemingly fails altogether before 
Burlington is reached. Its southern extension is not known. It 
is not believed to be as extensive as Missouri geologists have 
generally supposed. The Lithographic limestone of southwest- 
ern Missouri is not thought to be the same. The apparent 
fading out towards the north is not an unusual phenomenon 
among the limestones of the region. Similar cases are known 
in the Missourian series, or Upper Coal Measures, farther west.* 
At Louisiana and Hannibal, the shales bearing the latter 
name have a thickness of about 70 feet. This thickness is 
maintained northward at least as far as Keokuk, as deep wells 
show. Beyond this point at Burlington a very similar shale, 
appears in the base of the river bluffs, having a thickness, 
including the upper sandy portion (Chonopectus sandstone of 
Weller-), of 185) feet, above) the tiverm levely | Shale) isuknowa 
to extend downward at least 150 feet more, making a total 
measurement, from the top of the Chonopectus sandstone, of 235 
eet 
The question has arisen as to how much of the Burlington 
section? can be regarded as representing the Hannibal shale. 
On fancied lithologic grounds solely it was early suggested by 
Worthen* and White’ that the earthy fragmentary limestone, 15 
to 18 feet thick, overlying the lower ‘yellow sandstone” (the 
Chonopectus bed ) was the northern extention of the litho- 
graphic ( Louisiana ) limestone of Missouri. This view has been 
recently again alluded to by Weller.® If this were the case all 
tProc. lowa Acad. Sci., Vol. VII, 1900. 
2Trans. Acad. Sci., St.Louis, Vol. X, p. 57, 1900. 
3Full detailed descriptions of the various sections here referred to will be found 
in the lately issued volumes of the lowa and Missouri geological surveys. 
4Geology Iowa, Vol. I, p. 206, 1858. 
5 Boston Jour. Nat. Hist., Vol. VII, p. 212, 1860. 
Trans. Acad. Sci., St. Louis, Vol. X, p. 123 1900. 
