524 Melis: J OGIANAUL, (UR CIE OIL OG VA. 
ing, provisionally at least, the Magnesian limestone series below 
the Saccharoidal sandstone as Cambrian. The facts requisite 
to a final conclusion as to whether or not this line is the 
correct divisional one must be derived from a consideration 
of abundant fossils after a careful stratigraphic connection of 
the various sections has been made. In making a com- 
parison of the Magnesian series with the Cambro-Silurian of 
Iowa and Minnesota it may be noted that according to the recent 
work of Hall and Sardeson? the line between the Cambrian and 
Ordovician (Lower Silurian) is carried up to the base of the St. 
Peter sandstone, where a very distinct faunal break occurs. The 
Middle Cambrian is also recognized. This narrows down the 
space between the Cambrian and the Trenton limestone m that 
region to still smaller dimensions, so that if the inference is ¢or- 
rect only a thin sandstone now intervenes. If, further, the cor- 
relation by Worthen? of the St. Peter formation of northern 
Illinois and the sandstone at Cap-au-Grés, near the mouth of the 
Illinois river, and that sandstone with the Saccharoidal of Mis- 
souri is right, there is added further weight to the existence of 
the unconformity at the base of the latter. 
Regarding the age and history of the Ozark uplift much 
might be said. Since it is quite probable that the Archean peaks 
of southeastern Missouri formed the first land in the region 
to appear above the waters of the continental ocean it has 
been the general opinion among those who have worked in the 
district that the crystallines remained above sea level as an archi- 
pelago from pre-Cambrian times until the close of the Paleozoic 
when all the area around became a land surface. This has led 
to the inference that the existing geographic features are very 
old. But the validity of these conclusions is not only very ques- 
tionable but itis manifest that the present features of the Ozarks 
are essentially modern. 
It is probable that from Archean times the region has been 
one of constant oscillation, for the most part slight, perhaps, but at 
*Bul. Geol. Soc. America, Vol. VI, p. 170. Rochester, 1865. 
2Geol. Sur. Illinois, Vol. I, p. 150. Springfield, 1866. 
