70 



GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



The upper sandstones of this group are distinguished from the overlying 

 Triassic rocks by a deeper color, approaching a Venetian red, whereas in 

 the latter the color is rather of a light brick red. 



Plate V (p. 60) shows a remarkably contorted specimen of impure 

 limestone of this horizon from the outcrops on Empire hill, where abun- 

 dant fossils were found. 



Fossils. Fossil remains were found in various beds of this formation 

 in the Ten-Mile district; in a peculiar black limestone of the Hoosier ridge, 

 to the northeast of Mount Silverheels ; and on Empire hill, on the west 

 side of the range, adjoining Weston fault. 



From ten different localities in these regions the following forms were 

 obtained : 



Productus costatus. 

 Producing Nebrascensis? 

 Productus Prattenana. 

 Productus cora. 

 Spirifera Bockymontana. 

 Spirifera (Martinia) lineata. 

 Spirifera camerata. 

 Athyris subtilita. 

 Streptorhynchus crassm. 

 Chonetes Glabra. 

 Bellerophon crassus. 

 Bellerophon percarinatus. 

 Bellerophon (sp. ?). 

 Microdon tenui-striatum (very small). 

 Microdon obsoletum. 

 Pleurophorus occidental IK. 



Pleurotomaria (like P. Qreyvillewis). 

 Xaticopxiii (like y. Altonensis). 

 Macrochcilw (primigenius ?). 

 Nucula (tentricosa t). 

 Nucula (like N. Beyriche). 

 Microdoma (nearly M. conica). 

 Euomphalus (sp. !). 

 Archfeoccidaris (sp. t). 

 Astartella (8p. ?). 

 Loxomena (sp. t). 

 Fenestella (sp. t). 

 Murchinonia (sp. f). 

 Synocladia (sp. t). 

 Nautilus (sp. ?). 

 Entolium (sp. t). 

 Amplexm (sp. !) 



MESOZOIC. 



As Mesozoic beds do not occur within the area of the map, no attempt 

 was made to study them systematically or to obtain a measurement of 

 their thickness, which would have taken a great deal of time and probably 

 been impracticable without a more detailed map than could be had, Their 

 aggregate thickness has therefore been assumed to be not less than GjOOO 

 feet, a safe estimate judging from the thicknesses given by the geologists 

 of the Hayden Survey for various parts of Colorado. 



