NOMENCLATURE OF SOME CAMBRIAN TRILOBITES 



By CHARLES ELMER RESSER 



Curator, Division of Invertebrate Paleontology, 



U. S. National Museum 



INTRODUCTION 



After many years devoted to intensive study of Cambrian stratig- 

 raphy and paleontology, the author hopes soon to submit for print- 

 ing a complete summary of available information on the subject. Dur- 

 ing the course of this research many interesting facts have been 

 brought to light, and it becomes clear that much of the paleontology is 

 not up to date. To include the necessary nomenclatural changes in 

 the bibliographic portion of the summary would be to bury them ; 

 hence it is planned to pui:)lish, from time to time, separate papers 

 embodying necessary changes. 



Dr. Charles D. Walcott's intention to monograph the Cambrian 

 trilobites as he did the brachiopods was repeatedly stated in his writ- 

 ings and discussed in conversation over a period of many years. He 

 finally came to realize that this would be more than a life-long work, 

 since, while brachiopod species are numbered by hundreds, the trilo- 

 bites comprise thousands. Unfortunately, just as he was well started 

 on the description of the many new species in hand, matters pertain- 

 ing to the World War robbed him of his research time. Although he 

 accomplished much in this line, his assemblage of trilobites was so 

 vast that many of the species remained unstudied and undescribed. 



With the study of the new material generic relationships formerly 

 obscure become apparent, and a more satisfactory classification 

 emerges. However, monographic studies of many more groups must 

 be made before families or other groupings above generic rank can 

 be attempted. For this reason the genera discussed in this paper are 

 not referred to families. 



The data here presented do not lend themselves to precise syste- 

 matic arrangement, for time is not available to properly monograph 

 the genera or families discussed ; wherefore the information is given 

 in a condensed form, and is arranged alphabetically by genera. How- 

 ever, occasionally rather lengthy descriptions are presented, particu- 

 larly when important generic questions are involved. Usually incom- 



Smithsonian Miscellaneous Collections, Vol. 93, No. 5 



