6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
riam, U. S. Geological Survey, furnished much information on stratigraphy: in 
Nevada. 
Thanks are extended to two companions of several field expeditions, Dr. Byron 
N. Cooper and Dr. Raymond S. Edmundson, both former members of the Vir- 
ginia Geological Survey. These expeditions with Dr. Cooper and our associa- 
tion during the 6 months he spent at the National Museum were informative and 
inspiring. 
Dr. Raymond S. Edmundson, now of the University of Virginia, and a col- 
league of Dr. B. N. Cooper in the mapping of the Virginia chemical limestones. 
accompanied us on several expeditions. His brilliant and careful structural and 
stratigraphic work was of valuable assistance; he helped lay the groundwork of 
the stratigraphy. 
LOCATION OF TYPES AND ABBREVIATIONS 
Most of the types illustrated in this monograph belong to the U. S. National 
Museum. It was desirable to illustrate specimens borrowed from other institu- 
tions to show structures or species not exhibited in National Museum specimens 
or present in the National Collection. All the type repositories are designated 
herein, as follows: 
A.M.N.H. American Museum of Natural History. 
Carnegie Mus. Carnegie Museum. 
Columbia Univ. Columbia University. 
G.S.C. Geological Survey of Canada. 
M.C.Z. Museum of Comparative Zoology, Harvard College. 
U.S.N.M. United States National Museum. 
Y.P.M. Peabody Museum, Yale University. 
In the descriptive part of the monograph all numbers are those of the National 
Museum unless otherwise designated. In some cases, U.S.N.M. is prefixed to 
numbers where ambiguity might otherwise appear. 
In lists, names marked by an asterisk are doubtful identifications. 
NOTES ON THE CORRELATION CHART 
Any chart depicting correlation of formations is really only a report of prog- 
ress that approximates but never portrays the real truth. The chart presented 
herewith (chart 1, facing p. 130) is certainly not a final picture of this part of the 
Ordovician. Many parts of it are not in clear focus and it will take much study 
and more collecting of fossils to eliminate these fuzzy portions. Throughout all 
the Ordovician covered by this chart, much paleontological work still needs to 
be done. One of the important weaknesses in our knowledge of brachiopods is 
the small amount of information that has been gleaned on this group from the 
Table Head series of Newfoundland. The correlative rocks in Nevada are also 
in need of attention. With the appearance of this monograph the Appalachians 
will be better known, but many parts of them have not been studied and still 
remain virtually unknown. 
