CHAPTER XII. 



PALEOZOIC FOSSILS. 

 Section I.— CAMBRIAN FOSSILS. 



By Charles Doolittle Walcott. 



The Cambrian fauna of the Park includes 10 species that are referred 

 to the upper division, and 21 that are referred to the middle and lower 

 divisions, of the Middle Cambrian fauna. Of these, Acrotreta gemma is 

 common to the upper and middle divisions. The Middle Cambrian fauna 

 includes the following species: 



Haguia spbrerica. 



Obolus (Lingulepis) acurriinatus var. rueeki. 



Ipliidea sculptilis. 



Iphidea (sp. uudet.). 



Acrotreta gemma. 



Platyceras primordialis. 



Hyolithes primordialis. 



Agnostus bidens. 



Agnostus iuterstrictus. 



Agnostus tumidosus. 



Ptycboparia peufieldi. 



Ptycboparia antiquata. 



Ptycboparia (sp. undet.). 



Crepicephalus texanus. 



Ptycboparia (Loncbocepbalus) hamulus 1 



Ptycboparia (Loncbocepbalus) wiscousensis. 



Ptycboparia (?) diademata. 



Arionellus (sp. uudet.). 



Liostracus parvus. 



Soleuopleura weedi. 



Zacantboides (sp. uudet.). 



Batbyuriscus '? (sp. undet.). 



This fauna is more intimately related to that of the Black Hills and 

 the Upper Mississippi Valley in Wisconsin and Minnesota than to the Middle 



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