64 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 75 



INTRODUCTION 



The collections of invertebrate fossils in the United States National 

 Museum from the Cambrian and Ozarkian formations of the United 

 States and Canada contain a large and varied series of trilobites, 

 many of which are undescribed, while others have been given only 

 provisional study and publication. 



These collections have accumulated during the past 25 years, largely 

 as the result of my studies of the various formations of the Cambrian 

 and Ozarkian in western America. In the actual collecting, I have 

 been aided by several assistants, notably Dr. Cooper Curtice, Mr. F. 

 B. Weeks, Dr. L. D. Burling, Dr. Charles E. Resser, my two sons, 

 Sidney and Stuart, and their mother, and during the past 10 years, 

 Mrs. Mary Vaux Walcott has been most helpful in assisting me in 

 gathering the faunas of the lower Ozarkian and Cambrian in the 

 Canadian Rockies. During this period over 65,000 specimens have 

 been deposited in the Museum from collections made in the Cordil- 

 leran area alone. Many specimens have been contributed and loaned 

 by local collectors, and the generous cooperation of the Geological 

 Survey of Canada has been of great service through assistance in my 

 field-work and in loaning specimens for study. Dr. E. O. Ulrich has 

 gathered a great quantity of material from the Lower Paleozoic 

 formations of the Appalachians and the Mississippi Valley, in con- 

 nection with his field studies as a member of the U. S. Geological 

 Survey. From time to time he has made many intensive studies of the 

 fragmentary trilobites but refrained from publication in order to 

 obtain a more comprehensive knowledge of the faunas and the for- 

 mations in which they occur. I pursued a somewhat different course, 

 as it was essential that a few at least of the fossils occurring in the 

 great Cordilleran sections should be made known to the geologist. 

 This has led to much preliminary study and publication, since other- 

 wise the entire work would have been delayed for many years. Now, 

 thanks to the enthusiastic work of Dr. Charles E. Resser, aided and 

 checked by Dr. Ulrich, the great collections are being systematically 

 worked, studied and prepared for future publication. 



At the present time Dr. Ulrich is actively engaged in preparing 

 descriptions of the Ozarkian fossils together with a volume on the 

 stratigraphy. It is expected that portions of both volumes will be 

 ready for the press within a few months. Dr. Ulrich and Dr. Resser 

 are also carrying forward their studies of the Cambrian faunas of 

 the Mississippi Valley. Prof. B. F. Howell of Princeton University 

 and Dr. Resser also have under way a monographic study of the 



