80 lite American Geolf>;/isf. February, 1895 
oi' emergence still longer ainl would make the almost com- 
plete removal of the Algoiikiaii beds more readily understood. 
It is, however, possible that this land surface was only about 
the St. Francois mountains, and that Cambrian beds now 
exist in the deep basins away from here, especially to the 
northeast. Of this we have no local evidence to present, how- 
ever. 
I'/ie Si/i(rlav J*erio<L — P^arl}' in the Silurian, or possibly 
before the end of the Cambrian, well nigh the whole of Mis- 
souri must have been submerged and the deposition of the 
rocks of the Ozark stage was begun. Before the end of the 
Lower Silurian epoch it is probable that a re-elevation took 
place, exposing a large land surface to erosion. We conclude 
this because we are of the opinion that the Trenton and 
higher Silurian strata never covered the whole Ozark area. 
There is no positive evidence of their former existence there. 
The absence of any remnant or outlier, and also the absence 
of these rocks between the Devonian and Lower Silurian for- 
mations of the extreme southwest are both facts opposed to 
the idea of this extension. The same applies to the Crystal 
Cit}^ sandstone, though to a less degree. Lithologically this 
formation has more the character of a fluvial or estuary de- 
posit than of a wide spread sandy stratum. The flow struc- 
ture or false bedding frequently exhibited is in harmony Avith 
this idea. The unconformity with untlerl^nng rocks, exhib- 
ited at many localities, shows that an erosion period preceded 
its deposition. 
At the end of the Silurian period most of southern Missouri 
or of the Ozark uplift was, without much doubt, well above 
water level. 
'The Devonian Period — appears to have been essentially one 
of emergence in southern Missouri and to have remained so 
throughout. As with the Trenton and Upper Silurian strata, 
there is no positive evidence, in the nature of outliers or re- 
siduary products, of the former presence of Devonian rocks 
over the Ozarks. Along the western border of the uplift the 
formation is also absent between the Ozark stage of the 
Lower Silurian and the overlying Lower Carboniferous strata, 
with the exception of where the Eureka shale comes in, in Mc- 
Donald county. Similarly, they are absent along most of the 
