Io SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
paleontological information. Inasmuch as the present work is concerned wholly 
with brachiopods, stratigraphic discussion and correlation are based almost 
wholly on them. The bearing on correlation of fossils other than brachiopods is 
mentioned only in instances in which brachiopods tell an inaccurate or equivocal 
story. 
The lists of brachiopods appearing under the formation names have been ob- 
tained from the studies recorded herein and from lists published by other authors. 
In some instances listed identifications are so fantastic that the writer has placed 
an asterisk before the name to show that the identification is incorrect. For 
example, some Richmond species have been identified in the Simpson group. 
In many instances, however, I have not seen specimens recorded for all the 
formations and can only let the names stand even though considerable suspicion 
of incorrectness may attach to the identification. This naturally detracts from 
the value of the lists, but in any study of paleontological literature it must be 
realized that listed forms must be used with great care. This is especially true 
of the lists presented by the nonspecialist stratigrapher, who still feels that he 
can identify any fossil. 
In spite of the deficiencies noted above, the lists do contain the names of all 
species I have identified or described. These also appear in a master list at the 
head of the section on the brachiopods, but it will not be possible to check the 
species appearing in the stratigraphical section with those in the brachiopod part 
because the master list contains only species considered in the text. 
The formation lists are notably incomplete in some instances. All the forma- 
tions have not been evenly collected, and the need for some formation names 
became apparent only at a late stage of the work. Consequently, lists for the 
Sequatchie Valley formations, for example, are not entirely satisfactory, and the 
same situation exists with most of the marbles. Specimens from the marbles are 
usually difficult to identify because of exfoliation of shell, lack of preservation 
of muscle scars, and generally poor interior preservation; consequently, the age 
of the marbles was obtained by blocking them in between well-studied beds above 
and below. Furthermore, the faunas of the marbles are very much the same in 
generic composition, a remarkable example of facies restriction, which makes 
the identification of an isolated marble a difficult proposition. At present the 
marbles cannot be taken out of their sequences and satisfactorily identified or 
their age determined. They must some day be studied individually. 
Most of the lists suffer from incompleteness. This study has taken a long time 
and a huge collection was examined. Nevertheless, the collection on which it is 
based represents only a minute fraction of the fossils that must be collected and 
studied in the future to determine the true story of Ordovician stratigraphy and 
paleontology. It is at best a good beginning. 
The brachiopods discussed in this monograph come from the following regions: 
Newfoundland. 
The St. Lawrence and Ottawa Valleys and adjacent areas. 
The Champlain, Mohawk and Hudson Valleys. 
The Appalachians (Pennsylvania to Alabama). 
