white.] LAEAMIE FOSSILS OF BITTER CREEK VALLEY. 215 



The uppermost fossiliferons layer of the Laramie Group, doubtless 

 equivalent with the fossiliferous horizon both, at Point of Bocks Station 

 and in Yampa Valley, was found in the hill just west of the village of 

 Bock Springs, wliere I obtained only one species, Ostrea glabra Meek & 

 Hayden. The fossils of the following list were obtained at other and 

 lower horizons in the group just east of the village : 



LIST OF LARAMIE FOSSILS COLLECTED AT ROCK SPRINGS, WYOMING. 



1. Ostrea glabra Meek & Hayden. 



2. Anomia micronema Meek. 



3. Yolsella (Bracliydontes) regularis White. 



4. Corbula undifera Meek. 



5. Melanin insculpta Meek. 



~So other fossils were obtained from the Laramie strata on the west 

 side of the Aspen Mountain Uplift, but important collections were made 

 from them at three localities upon the east side. The first of these local- 

 ities is about two miles below or west of Point of Eocks Station, where 

 the following fossils were obtained : 



LIST OF LARAMIE FOSSILS FROM BITTER CREEK VALLEY, TWO MILES 

 WEST OF POINT OF ROCKS STATION, WYOMING. 



1. Ostrea glabra Meek & Hayden ? 



2. Anomia grypliorliynchus Meek. 



3. Corbicida cytheriformis Meek & Hayden. 



4. Corbula subtrigonalis Meek & Hayden (=C. tropidopliora Meek). 



5. Melania insculpta Meek. 



6. Odontobasis buccinoides White. 



The exposure here is only a very limited one of a single stratum of fos- 

 siliferous rock, being the same as that from which Mr. Meek collected his 

 type specimens of Anomia gryphorhynchus. The position of this fossilif- 

 erous horizon in the Laramie series is probably about the same as that 

 just east of the village of Eock Springs, although most of the fossils are 

 of different species. 



The fossiliferous horizon at Point of Eocks station, two miles farther 

 up the creek, holds a position several hundred feet above the one in ques- 

 tion. Just how much higher in the series it belongs could not be ac- 

 curately known, because there is an unconformity of the strata between 

 the two horizons. This unconformity is evidently of limited extent in 

 this district and has probably not greatly affected the aggregate thick- 

 ness of the whole group. I could find no trace of it in the Laramie strata 

 of the valleys of Yampa and White Eivers, but Professor Powell has re- 

 ported it to exist elsewhere, and upon it he made the division between his 

 Point of Eocks and Bitter Creek groups. I adopted his views in this re- 

 spect in my report upon his collections, in the third chapter of his Eeport 

 on the Geology of the Uinta Mountains ; and also in my Paleontological 

 Papers ]Sbs. 2, 3, and 5 in the Bulletin of the United States Geological 

 and Geographical Survey of the Territories. Subsequent investigations, 

 however, show that the paleontological characteristics of the strata 

 above and below this unconformity are too nearly identical to admit of 

 their separation as belonging to separate epochs, even if that uncon- 

 formity were general instead of local. 



The fossibferous horizon at Point of Eocks station is the uppermost 

 one of the group that is yet known, and is essentially the same as that 



