SOUKCES OF INFORMATION. 371 



region in Nevada, and also at Washoe, and which we have abundant 

 evidence to prove extends over a vast area on the Pacific coast. * 



Earlier Explorations of the United States Geological Survey. — The writer's 

 first excursion through this region was made in 1885, and the results 

 appeared in the United States Geological Survey Bulletin number 33 

 and in the 8th Annual Report of the Director of the United States Geo- 

 logical Survey, pages 401-432 ; but the detailed study of the region was 

 not systematically undertaken until 1890. 



In the meantime the region was visited on different occasions by 

 Mr. I. C. Russell, Professor Hyatt, Mr. II. W. Turner, and Dr. Cooper 

 ( lurtice. The extensive collections made in 1887 by Professor Hyatt and 

 Mr. Russell, who spent several weeks in the region, were obtained chiefly 

 from two horizons in the Jura and in the Trias ; but since that time, in 

 L890 and 1891, Professor -Hyatt has spent several months with me in the 

 field and made still larger collections from all the horizons in the Jura 

 and Trias, as well as from a number of older formations. Too great 

 praise cannot be given him for the assistance his paleontologic studies 

 in tie- Held have rendered me in working out the structure of tins com- 

 plicated region. Dr. Curtice was in the region nearly three weeks in 1890, 

 and discovered a number of new fossiliferous rocks. From Ins collections 

 Mr. Walcott determined the presence of the Silurian and Carboniferous, 

 while Professor Hyatt recognized a new horizon in the Jura and the 

 paleobotanists identified certain slates as Mesozoic. 



TOPOGRAPHY OF THE TAYLORVILLE REGION. 



The Taylorville region, as referred to in this paper, embraces an area 

 about 12 miles in Length, from northeast to southwest, and 6 miles in 

 width. 



To the northeast the region is limited by Keith' rock and the divide at 

 the head of llosselkus creek-; to the southwest by Grizzly mountain, 

 Hough peak, and Arlington heights, extending to American valley and 

 Spanish creek. .Mount Jura, so named on account of the Jurassic age of 

 the rocks it contains, lie- near the center, directly between Taylorville 

 and Genesee. Other important localities referred to are Foreman and 

 Peters ravines, which join (he northern arm of Indian valley from the 

 east : Hinchman ravine, on the eastern slope of mount Jura, and Hornfels 

 point . immediately north of ( ieiiesce valley, opposite the school-house. 



FORMATIONS OF THE TA YLORVILLE REGIOA 



Sedimentary Formations. — The accompanying table gives a summary of 

 the geologic components of the Taylorville region. Thr< f the greal 



- • also "Auriferous Gravels of the Sierra Nevada of California ' (Memoirs Mus, 

 ' on,].. Zool, .ii II • • vol. vi) 1879, pp. 39 and W, 



