REPORT OF DEPARTMENT OF INVERTEBRATE FOSSILS. 207 



very c()mi)leto series of species, and still further increase tlie miinber 

 of species coiumou to the eastern and central (or Atlantic and Missis- 

 sippi) areas and the western orEocky Mountain area. 



"The fauna of the Upper Carboniferous- limestone is composed of 

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

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

 Ftiloilictya Carbonaria, F. serrata, and Macrodon tcmiisfriafa. 



"There is a certain coniniingling of Ui^per Devonian species with 

 the Lower Carboniferous fauna. We find Discina Neicherryl, Macrodon 

 Hamiltonw, Grammysia Hannibalensis, 0. areuata, t^anguinoJitefi JEohis, 

 and Pkuroiomaria nndomaryinata, associated with common Carbonifer- 

 ous species. 



"The discovery of Pulmoniferous mollusks of the genera Physa and 

 Zaptychius in association with the fresh-water shell AmjjiiUaria roiceUi 

 and fragments of a flora conil'erous 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 iu rocks of this age; the land shells of Nova Scotia and Illinois 

 occur in the Coal Measures, and Strophites grandceva, Dawson, is from 

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

 discovery on the i)resence 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. 



"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 

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

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

 Annual Report 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 : 



