NEW LOWER AND MIDDLE CAJ^IBRIAN CRUSTACEA 



By Charles E, Resser 

 Associate Curator of Stratigraphic Paleontology 



INTRODUCTION 



Among the numerous Cambrian fossils that have been accumulating 

 in the United States National Museum during the last 15 years, 

 there are many undescribed species and some of the specimens are 

 remarkable for the preservation of thin tests or of soft body parts. 

 In order to stimulate further search for the rarer fossils, and par- 

 ticularly for preservations of the softer parts of animals or of delicate 

 plant tissues, it is planned to publish more or less related groups of 

 these animals from time to time. Accordingly, in this paper I have 

 assembled a group of species that centers mainly around the pre- 

 viously described genus Tuzoia, but which also includes several unre- 

 lated forms that were secured from the same localities as the others. 

 This paper thus adds several new species preserving more than 

 ordinarily thin tests of Crustacea and a few with the still softer 

 fleshy parts. Some are from the well known Burgess shale that has 

 already furnished so many interesting animals and plants, but 

 other formations, some of which have not previously been known to 

 yield such fossils, are also represented. 



This paper also contains information of interest aside from that 

 naturally attaching to any description of the softer parts of such 

 ancient animals, by presenting certain important stratigraphic facts 

 in addition to further data regarding the geographic distribution and 

 origin of the faunas to which these species belong. 



Acknowledgment. — In the preparation of this paper I was kindly 

 assisted by Dr. E. O. Ulrich in the matter of specific determinations 

 as well as by much appreciated general criticism. 



The Pennsylvania specimens of Tuzoia all belong to the Getz- 

 Collection in the Peabody Museum, Yale University. I was per- 

 mitted to describe the two species represented, through the extreme 

 kindness of Dr. Carl O. Dunbar, who had previously planned to 

 describe them himself. 



No. 2806.— Proceedings U. S. National Museum, Vol. 76. Art. 9 



62996—29 1 1 



