PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 9 
characterized by abundance of Opikina, Strophomena, Pionodema, and Dole- 
roides. It is succeeded by the Trenton with its flood of cryptolithid trilobites 
and more modern brachiopods, many of which appear in the preceding stage but 
fail to make a prominent impress on the fauna. The Oranda fauna is believed to 
have lived in Wilderness time and represents the fading stages of the Porterfield 
fauna, which lingered on in eastern areas probably now obliterated by the intru- 
sions of the Blue Ridge and Great Smokies and the metamorphism of sediments 
now underlying the Piedmont. 
Trenton stage.—This stage is modified by removal of the Rockland which has 
mostly fossils derived from the underlying Black River and Witten. Deposition 
of the Sherman Fall is thought to inaugurate the Trenton stage. 
The chart also gives the range of the important genera described. A star 
indicates that the genus appears as far as known at present, at the point where 
the star appears, and then ranges to a point beyond the upper limits of the chart. 
An asterisk behind a generic name or group of names means that the genera 
do not range beyond the point where the asterisk occurs. A number of genera 
so marked are confined to the Pratt Ferry formation. Numbers are placed at 
the top and bottom of the chart to make the finding of the generic name in any 
column easier. In the annotated list of genera and species appearing in Sec- 
tion II each genus bears the number of the column in which it appears. 
GEOGRAPHIC AND GEOLOGIC SETTING OF THE FORMATIONS 
In the following pages are set forth brief descriptions of the formations from 
which were taken the brachiopods forming the subject of this report. The geo- 
graphic setting for the formations is given according to the region or realm in 
which they are developed. In the Southern Appalachians the stratigraphy is so 
complicated and the formations so numerous that it seemed advisable to arrange 
the formations alphabetically and reserve the regional discussion for the com- 
panion paper to the present volume being prepared by B. N. Cooper and myself. 
That discussion will consider all the Southern Appalachian formations from 
Pennsylvania to Alabama in detail. Most of that information need not be given 
here, but for the sake of completeness the formations and their faunas are 
described and listed. 
My field work has not been sufficiently extensive to cover all the regions from 
which Chazyan and related brachiopods have been taken. Some of the discus- 
sion is therefore based on the literature. This is true also of the fossil lists. I 
have not seen all the species listed under some of the formations, nor does the 
National Museum have collections from all the formations, but the names are 
recorded nevertheless. 
In discussing the formations, it seemed unnecessary to repeat any material 
already appearing in the “Lexicon of Geologic Names” (Wilmarth, 1938). This 
useful work contains the definitions of all formations described in the United 
States up to January I, 1936. Formations named after that time are herein 
described more fully. Although the definitions in the “Lexicon” are complete 
and some information on correlation is given, the book contains scarcely any 
