350 University of California Publications in Geology [Vol. 8 



horizontal shortening, through folding, seen in the beds. This last 

 conception does receive some support in the locally steep upturning 

 of the beds along the mountain flanks and around isolated masses of 

 the underlying older rocks outcropping in the valleys. This concep- 

 tion would, however, necessitate slipping movements, of considerable 

 magnitude, of the Esmeralda strata on the older rocks, and would 

 presume a tendency on the part of these beds to arch up and rise 

 away from the underlying rocks at the anticlines. It is not at all 

 clear how forces were effective to bring about the minor deformation 

 in the Esmeralda strata. 



Fauna, Age, and Correlation. — The fossil remains obtained from 

 the Esmeralda beds in lone and Stewart valleys comprise a consid- 

 erable quantity of mammalian bones, a few fish bones, the shells or 

 easts of several species of fresh-water molluscs, and fossil wood. 



Fossil mammalian remains, in the form of single bones or of groups 

 of more or less scattered and disjointed bones representing single 

 individuals, were collected from numerous localities and horizons in 

 the Esmeralda strata in both lone and Stewart valleys. Ungulate, 

 carnivore, and rodent forms are abundantly represented in the fauna 

 obtained. Remains of species of horses and camels make up a large 

 part of the fossil material. 



The bone surfaces are often checked and cracked, indicating ex- 

 posure to the elements before burial. The remains are most abundant 

 in sandstones and in ashy deposits ; a portion of a single connected 

 skeleton was found in limestone. A few specimens were found in beds 

 of coarse angular terrestrial material. The usually scattered distri- 

 bution of the skeletal parts, the weathered surfaces of the bones, and 

 the commonly rather coarse or ashy nature of the enclosing materials, 

 indicate that the burial of the mammalian remains occurred mainly 

 under conditions of terrestrial or shore deposition. 



The mammalian fossil material collected in the Esmeralda beds 

 in Stewart and lone valleys has been studied, by Professor J. C. 

 Merriam. and the age of the fauna represented by the material deter- 

 mined as approximately upper Miocene. In a forthcoming paper 

 Professor Merriam compares the age of this fauna with that of faunas 

 obtained from other Neocene beds of the Great Basin — the Mascall and 

 the Rattlesnake formations of the John Day Basin in north central 

 Oregon, the Virgin Valley and Thousand Creek beds of northwestern 

 Nevada, and the Mohave beds from the eastern, and the Ricardo 

 beds from the northern, parts of the Mohave Desert (see pi. 32). 



