REPORT OF DEPARTMENT OP INVERTEBRATE PO88IL& 207 



very complete series of species, and still farther increase the Dumber 

 of species OOtnmOD to the eastern and central (or Atlantic ami Missis 

 sippi) areas and the western or Rocky Mountain area. 



"The fauna of the Upper Carboniferous limestone is composed of 

 old and well-known species usually occurring at that horizon, and gives 

 bat three species new to the region of the Rocky Mountains, viz, 

 Ptilodictya VarboiHuia, P, svrrata, ami Macrodon tcnuistriata. 



"There is a certain commingling of Upper Devonian species with 



the Lower Carboniferous fauna. We And DUoina Newberryij Maorodon 



Jlamiltoniv, GrdHunysia Hannibalensis, (}. arcuata, S<ut</uinolths Jutlus, 

 and Pleurotomaria nodomarginata, associated with common Carbonifer- 

 ous species. 



u The discovery of Pulnioniferous inollusks of the genera l'hvsa and 

 Zaptychius in association with the fresh-water shell AmpuUaria Poicclli 

 and fragments of a flora coniferous in character, supports the strati 

 graphic evidence of the presence of a near or not distant land area at 

 the time of the deposition of the Lower Carboniferous rocks of Central 

 Nevada. It also gives the first notice of the occurrence of the Pulmon- 

 ifera in rocks of this age; the land shells of Nova Scotia and Illinois 

 occur in the Coal Measures, and Strophitea grandwva, Dawson, is from 

 the Devonian plant beds of New Brunswick. The bearing of this 

 discovery on the presence of land areas from the time of the Middle 

 Paleozoic to the present is important. No other explanation offers than 

 that there was a continuous fresh-water habitat, ponds or streams, 

 which permitted the species to descend in a direct line from Paleozoic 

 time to the present. 



u The grouping of the genera and species in the strata is shown in 

 a general manner in the systematic list at the end of this volume, and 

 iu greater detail in the abstract of a report on the geology of the 

 Eureka district, Nevada, by Arnold Hague, contained in the Third 

 Annual Eeport of the Director of the U. S. Geological Survey." 



In the accompanying table the number of species known at present 

 in the Paleozoic formations of Central Nevada is given : 







^ 



1 















£> 









Formation. 







8 . 



CO ~ 



i 

 1 



Pi 



00 



1 



CO 



P. 



■ 



a 





2 



§ 



1, 



> 

 2 



■ 

 * 



1 



a 



I 





O 



a? 



£ 



* 



P 



■-■■ 





24 



69 



:;-j 



31 



6 





Silurian: 





Pogonip 



47 



99 



34 



31 



34 



v., 



Trenton, <fcc 



14 



15 



4 





11 





Devonian 



102 

 65 



225 



132 



119 

 53 



61 

 50 



4f> 





Carboniferous 



3 







Total 



252 



8 



540 



1H 



242 

 18 



173 



125 



18 















Total f 



244 



522 



224 



173 



125 









