NO. 3 UPPER CAMBRIAN TRILOBITE FAUNAS — RASETTI 3 



Survey 7j^-minute quadrangles at the scale of 1 :24,000. Localities 

 are always indicated herein by coordinates (x = abscissa, y =: ordi- 

 nate) in millimeters, measured from the southeast corner of the map. 



The present study has been limited to trilobites. In the Dresbachian 

 formations of Tennessee the brachiopods are, as usual, the next in- 

 vertebrate group in order of abundance. The phylum is represented 

 mostly by inarticulates. Recent studies, such as those by Palmer 

 (1954) and Bell and Ellinwood (1962) in Texas, have shown that 

 adequate investigation of these fossils requires extensive etching of 

 limestone with acetic or formic acid, since mechanical preparation 

 generally yields only the exterior of the shell, of scarce taxonomic 

 significance. It is possible that etching of large amounts of limestone 

 of the Aphelaspis zone — the only portion of the Upper Cambrian in 

 the area where brachiopods are relatively abundant — might yield 

 interesting results. For a number of reasons such a program was not 

 undertaken. 



The other invertebrates observed are indeterminable echinoderm 

 plates, fairly common in certain beds but poorly preserved; a small 

 gastropod of the " H elcionella" type, and a few dendroid graptolites in 

 shale beds. The description of these groups of fossils would not bring 

 any significant contribution to paleontology. 



ACKNOWLEDGMENTS 



The present work was started as part of a research project under a 

 grant from the Penrose Bequest of The Geological Society of America. 

 This grant had already produced two papers (Rasetti, 1959, 1961) 

 on the Cambrian of the central Appalachians, When funds from this 

 source were no longer available, the work was continued and com- 

 pleted with grant No. 2829-P from the Penrose Fund of the American 

 Philosophical Society. The author is greatly indebted to both institu- 

 tions for their support. 



Thanks are also due to Dr. Allison R. Palmer for valuable discus- 

 sions on problems of taxonomy and biostratigraphy and for communi- 

 cating unpublished results of his investigations in the Upper Cambrian 

 of the western United States; to Dr. Robert B. Neuman for strati- 

 graphic information ; and to Dr. Charles R. L. Oder for communicating 

 his unpublished measurements of sections and for accompanying the 

 author in some field excursions. 



DESCRIPTIONS OF LOCALITIES AND SECTIONS 

 GENERAL STATEMENT 



This part of the paper presents the stratigraphic evidence that was 

 used in arranging the Upper Cambrian faunules in their proper time 



