LOWEE COAL MEASURE FAUNA. 171 



of beds. From this data the developmeut of the Lower Coal-measui*e 

 epoch at Eureka is placed at 3,800 feet ; this thickness is probably rather 

 under than over estimated. 



Region South of Spring Hill. Aloug' the di^^de wliicli sepai'ates Spring Hill 

 from Carbon Kidge vast accumulations of andesites, rhyolites, pumices, and 

 basalts have poured out, submerging over a large area all sediiiuiitary 

 beds. An exception is found in the broad, deeply eroded basin just nortli 

 of Pinto Peak, Carboniferous rocks again coming to the surface. 



Within this basin occurs several exposm'es of limestones, and on the 

 north side there is a short naiTOW ridge nearly 200 feet in height in which 

 the beds are seen to strike N. 24° W. and dip steeply to the east. At the 

 western end of these exposures there occurs a well defined belt of sand- 

 stones, beneath which crops out an area of clay shales. The latter are so 

 obscured by Quaternary accumulations that but little could be made out of 

 them. They resemble, however, similar shales to the west of Carbon Ridge. 

 The sequence of beds indicates their close relationship to those of Spring 

 Hill, but their geological age is still more strongly shown by the grouping 

 of fossils obtained from the limestones. The complete list is given here, as 

 it is rather a characteristic grouping of the Lower Coal-measures of Eureka 

 and carries with it a number of species found elsewhere in the district at 

 both lower and higher horizons. The list is as follows : 



Stromatopora, sp. ? Crenipecten liallanus. 



Zaphrentis, sp. ? Pterinea pLutocnsis. 



Syriugopora. Pinna consiinilis. 



rtilodictya. Myaliua subovata. 



Lingula mytaloides. Myalina congenciis. 



Ortbis I'esupinata. Modionioi])!);! ? pintocnsis. 



Cbouetes grauulifera. Sauguinolitcs retusus. 



Productus semireticulatus. Microdou connatus. 



Productus pratteuianus. Schizodus cuueatus. 



Spirifera camerata. Schizodus pintoensis. 



Spirifera striata. Belleroplion niajusculus. 



Eliynihonclla eurekensis. Orthoceras randolplieusis. 



Aviculopecten pintoensis. Ortboceras, sp. 1 



Aviculopccteu peroccidens. Leperditia, sp. ? 



Streblopteiia similis. Griffithides j>ortlocki. 



