168 
IOWA ACADEMY OF SCIENCE 
the coral Lithostrotion canadense, is continuous with the arenaceous or 
dolomitic beds now known to be of Salem age is incorrect. It is true that 
the arenaceous layers do often pass laterally into limestone, as has been 
stated, but this limestone is stratigraphically lower than the magnesian phase 
which sometimes occurs at the base of the true St. Louis and it is distinctly 
different both physically and faunally from that stratum. 
The common misconception as to the identity of the two formations has 
resulted, no doubt, from the stratigraphic position of sornetimes the one 
and sometimes the other just above the Keokuk or Warsaw. Apparently the 
unconformity which exists at the top of the Salem was not suspected by former 
workers in the field. 
In its typical development the Salem may be studied at Warsaw and Niota, 
lUinois, and at Augusta, and Lowell, Iowa. But many other localities which 
illustrate the stratigraphic relations of the formation could be cited. 
On account of the emergences which directly preceded and followed the 
deposition of the Salem in the region, this formation appears at no definite 
horizon and possesses a very inconstant thickness. Thus, instead of succeed- 
ing the Warsaw beds as in the normal sequence, the formation in various 
stages of development may rest upon an eroded surface of the Upper Keokuk 
(Geode bed), or may be completely wanting when the St. Louis rests upon 
beds sometimes as low as the Lower Keokuk (Keokuk limestone.) 
The fauna of the formation is noted principally for its fenestelloid bryozoans 
among which there are many genera and species. These, with a few brachiopods, 
the most important of which is a Productus closely resembling P. burlington- 
ensis, are the most prevalent fossils. 
BIBLIOGRAPHY. 
1. Gordon^ C. H. (1895.) Geol. of Van Buren county, (Iowa). Iowa Geol. Surv;, 
vol. 4, pp. 214-222. 
2. Keyes^ C. R. (1895) Economic Geol. of Lee county, (Iowa). Iowa Geol. Surv. 
vol, 8, pp. 345-352. 
3. SavagBj T. E. (1902) Geol. of Henry county, (Iowa). Iowa Geol. Survey, Vol. 12, 
pp. 262-284. 
4. Weller, S. (1907) 111. Geol. Surv. Bull. No. 6, pp. 24-25. 
5. Weller, S’. (1907) 111. Geol. Surv. Bull. No. 8, pp. 81-102. 
6. Bain, H. F. (1895) Geol. of Keokuk county (Iowa). Iowa Geol. Surv., Vol. 4, 
p. 279. 
7. Bain, H. F. (1896) Geol. of Washington county, (Iowa). Iowa Geol. Surv., Vol. 
5, pp. 149-150. i 
