58 GEOLOGICAL FORMATIONS 



AUGUSTA LIMESTONE. 



In a paper entitled " Carboniferous Echinodermata of the 

 Mississippi Basin," published in September, 1889,* it was pointed 

 out upon purely paleontological grounds, as well as for litholo- 

 gical and stratigraphical reasons, that the Burlington and Keo- 

 kuk limestones should be included under a single title, at least 

 along the line of the Mississippi river where the typical ex- 

 posures occur. At that time no name was proposed, for the 

 reason that it was not thought advisable until further investi- 

 gation was extended southwestward and southeastward from 

 the original localities, and the exact relations made out be- 

 tween the rocks as shown in the latter place and those of dis- 

 tant regions referred to the same age. Quite recently, however, 

 Williams t has suggested for this long-aeeded term " Osage." 

 This is the name of the river of western Missouri which cuts 

 through the lower Carboniferous series as represented in Saint 

 Clair county. 



As stated in the more recent publications in which the 

 name has appeared, " Osage " has been used for the Burlington 

 and Keokuk rocks of Missouri only provisionally — until more 

 detailed information could be obtained. The term Osage does 

 not now appear applicable, in the sense in which it was origi- 

 nally proposed, to the rocks of the Mississippi basin under 

 consideration. The Osage river, from which the name is taken, 

 flows for a greater part of its length through limestones of the 

 great Ozark series (Cambrian or Lower Silurian). The upper 

 part of the river passes through Coal Measure beds almost 

 entirely. Only a very small portion of the water-course touches 

 the Lower Carboniferous at all. The " Osage country," by al 

 Missourians especially, is a term applied to the region along 

 the lower part of this stream. At Osceola, where the most 

 typical section of the "Osage" is exposed, the rocks appear 

 to be as typical Burlington as at the city of Burlington itself. 

 Kecent visits have disclosed no Keokuk whatever at the place 



*Keyes: Am Jour. Sci., (3), Vol. XXXYIII, pp. 1S6-193. 1889. 

 tBal. U. S. Geol. Sar., No. 80, p. 109. 1891. 



