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University of California Publications in Geology [Vol. 13 



FAUNAS 



The fauna obtained from Bristol Mountain consists of several 

 species of trilobites and one species of brachiopod. All of the trilobites 

 with the exception of the Middle Cambrian form, Bathyuriscus, were 

 found in a thin bed of arenaceous shale in the Lower Cambrian and 

 all the species were so intimately associated that fragments of thoracic 

 segments could not definitely be differentiated. A similar confusion 

 was encountered in attempting to distinguish between fragments of the 

 hypostoma, consequently several of the species are based on the 

 cephalon only. 



Lower Cambrian. — The fauna of the Lower Cambrian consists of 

 four species of trilobite and one brachiopod. These forms represent 

 the upper part of the Lower Cambrian or the Olenellus zone. 



FAUNA OF THE LOWEB CAMBRIAN 



Mesonaois gilbert i, Meek. 



Olenellus fremonti, Walcott. 



Callavia = C. ? nevadensis, Walcott. 



Wanneria? eadizensis, n. sp. 



Mieromitra (Paternia) prospectensis, Walcott. 



Middle Cambrian. — Only one species that could be definitely 

 determined was found in the Middle Cambrian. Two or three speci- 

 mens similar to Bathyuriscus howelli were found near the top of the 

 massive shale of the Middle Cambrian. This species is probably new, 

 but the cephalons of all the specimens were crushed so that the original 

 characters could not be accurately determined. It is referred to 

 B. howelli as it has eight thoracic segments and seems to correspond 

 to this species excepting in the fifth segment, which is broader than any 

 of the others and terminates in a long spine that curves well back 

 toward the pygidium. It is therefore called B. howelli var. lodensis. 



Carboniferous. — The carboniferous is represented by numerous 

 fragments of rounded crinoid stems and faint outlines of corals 

 together with indeterminable organic remains. According to Mr. 

 Darton, the Carboniferous also contains Spirifer rocky montanus, 

 Michelina, sp., Cliothyridina?, sp., etc. 



