THE PRE-RICHMOND UNCONFORMITY 523 
much thicker bed. ‘That these few inches of clay, however, are in 
the main actually undisturbed is quite apparent, only the uppermost 
layer, a fraction of an inch in thickness, showing evidence of having 
been reworked by the waves, by reason of the mingling of. Maquoketa 
fossils. 
In passing southward this stratigraphic interval is next encoun- 
tered in St. Louis and Jefferson Counties, Missouri, and in Monroe 
County, Illinois. In none of this more southern area has such a 
striking instance of physical unconformity been observed as that near 
Batchtown, but the unconformity is none the less distinctly shown. 
The section in this region is slightly different from the Calhoun County 
section, by reason of the presence of the true Richmond with its Rhyn- 
chotrema capax fauna, and may be somewhat generalized as follows: 
t. Burlington limestone and Kinderhook beds, whose differentia- 
tion is not of importance in this place, resting unconformably upon 
the Maquoketa shale. 
2. Maquoketa shale, 4 to 30 feet in thickness, often with abundant 
graptolites in the higher beds, and with the typical Clezdophorus 
neglectus fauna at the base. This formation exhibits much variation 
in different vertical sections in the region, but it always contains the 
typical Maquoketa fauna. 
3. Richmond limestone, +2 feet in thickness. This is a hard, 
more or less impure limestone, somewhat darker colored than that 
below. It is abundantly fossiliferous, the most conspicuous species 
being Rhynchotrema capax. This bed is remarkably uniform in 
character, both lithologically and faunally, throughout this region of 
outcrop. 
4. Kimmswick limestone, +50 feet in thickness. The outcrop of 
this limestone along the Mississippi River in Jefferson County consti- 
tutes the typical expression of the formation. Itis remarkably uniform 
in all of its characters, with the same formation in Calhoun County. 
In any single vertical section in this region the physical uncon- 
formity between the Kimmswick limestone and the Richmond bed 
is not conspicuously exhibited, although the faunal change is sudden 
and complete.. In following the contact from the section at the rail- 
road cut one mile south of Kimmswick, however, to the quarry at 
Glen Park, and then in the sections of the river bluffs to an aban- 
