STRATIGRAPHY ALONG THE ROCKY MOUNTAIN TRENCH 363 



(3) Fossils were found only in one place, while in the other series 

 they were abundant. No attempt has been made to divide or 

 correlate the different members of the clastic series, because of the 

 great difficulty and the extremely detailed work necessary for 

 classification of unfossiliferous formations in a folded region. A 

 part of it is probably pre-Cambrian. 



In the limestone series fossils of the following ages have been 

 found : Upper Cambrian, Lower Ordovician, lower Richmond, upper 

 Richmond, Upper Devonian, and Mississippian. Also the Middle 

 Cambrian horizon at Elko might be considered as part of the 

 "limestone series." Other horizons, including portions of the 

 Silurian, are possibly present. Disconformities are common, 

 showing that there was considerable oscillation of the areas of 

 active deposition. Angular unconformities have not been found 

 but may occur. 



Stratigraphic sections were made at several localities along the 

 trench and some of the more representative have been combined 

 into a generalized section (Fig. 2). This section consists chiefly 

 of formations found in the vicinity of Sinclair Springs. 



Upper Cambrian and Lower Ordovician. — No stratigraphic break 

 has been observed between the Cambrian and Ordovician in the 

 northern portion of the trench visited. Fossils were collected 

 which have been identified by Dr. Walcott as belonging at the 

 top of the Upper Cambrian, and above this is a horizon containing 

 a fauna identified by Dr. Raymond as corresponding to the base 

 of the Ordovician in Europe.^ Walcott identified the following 

 species : 



Dicellomus sp. Crepicephalus ? fragments of 



Agnostus sp. cephalon 



Agnostus sp. Ptychaspis cf. striata Whitfield 



The species identified by Dr. Raymond included: 



Lingulella moosensis Cyphaspis brevimarginata 



L. allani Hemigyraspis mcconnelli 



Obolus molisonensis H. carbonensis 



Eorthis desmopleura Megalaspis shepardi sp. nov. 



E. sp. (ind.) Dalmanella hamburgensis 



' P. E. Raymond, Am. Jour. Set., fifth series, Vol. Ill, p. 204. 



