248 The American Geologist. April, 1902. 
which is used to include both the St. Louis and Chester or 
Kaskaskia of earlier authors. From the relationships of the 
faunas in the east it is not easy to determine to what portion of 
the Genevieve epoch the fauna belongs. The fauna of the 
Batesville sandstone in Arkansas, however, is closely related to 
these and it lies at the base of the Kaskaskia, just above the 
St. Louis, and it will probably be safe to assume that the age 
of the Pennsylvania and West Virginia faunas is about mid- 
Genevieve.” 
From the point of stratigraphy this conclusion would ap- 
pear to be correct, for above the limestone is the shale, attain- 
ing great thickness further south, which has yielded only Ches- 
ter forms. The Silicious limestone has yieldea no fossils at 
any exposure in southwest Pennsylvania, though carefully ex- 
amined at many places.’ I. C. White, however, found in it 
an imperfect Straparollus on the western side of the Broad 
Top basin. The rock was studied carefully under the micro- 
scope by Profs. Linn and Linton of Washington and Jefferson 
college, who discovered in it an abundance of Foraminifera. It 
consists of “grains of quartz, some of feldspar, and rounded 
grains of carbonate of lime, embedded in a matrix of carbonate 
of lime, and thus held together.”* | They emphasize the pecut 
iar character ot the rock which enables one to recognize it at 
once in well drillings by aid of a glass. It is unique micro- 
scopically as well as macroscopically. Southward its silicious 
material is less disseminated, more segregated, the rock be 
comes fossiliferous and its relations are with the St. Louis. 
One may object to this conclusion, that I. C. White found 
Chester fossils in the Shenango shales in northwestern Penn- 
sylvania and that the writer has regarded those shales as un- 
derlying the Silicious limestone. There is no difficulty here. 
The Shenango shales in Crawford county of Pennsylvania are 
beyond the extreme northwest limits of the limestone and in 
that region they must represent the whole sedimentation 
throughout the post-Pocono time; so that if the Chester sea 
extended so far north, one should expect to find Chester fos- 
sils in the shales. Just as the Chattanooga shales of Tennes- 
see, beyond the area in which Pocono and Chemung have dis- 
appeared successively, must represent for that region the whole 
*Second Geol. Surv. of Penn., Ann. Rep. for 1885, p. 223. 
