462 MINING INDFSTEY. 



some of the same fossils (Cardium, Inoceramus, and Ostrea), brought from 

 outcrops of this rock on Weber Eiver, in Utah, by the expedition under the 

 command of Captain (now Colonel) J. H. Simpson/ In 1861, I also de- 

 scribed, in connection with Dr. Hayden, the same Cardium, and an oyster, 

 found on Gros Ventres River, associated with one of the same species of 

 Inoceramus, by Captain Reynolds, referring them provisionally to the Creta- 

 ceous.^ 



The entire absence, so far as yet known, among the moUuscan remains 

 of this formation, of any species of Ammonites, Scaphites, Toxoceras, Hamites, 

 Ftychoceras, Turrilitcs, Heteroceras, or any of the various other types, (ex- 

 cepting Inoceramus, and perhaps Anchura) generally considered either char- 

 acteristic of the Cretaceous, or, in part, of that and older secondary rocks, 

 and unknown in the Tertiary, would seem to indicate, with the presence of 

 the latter types, that these beds belong to one of the very latest members of 

 the Cretaceous ; or, in other words, that they were probably deposited when 

 the physical conditions favorable to the existence of those forms of molluscan 

 life, peculiarly characteristic of the Cretaceous period, were drawing to a 

 close, or had in part ceased to exist. 



Collections from the Bear River Estuary Beds. 



No 1. OSTEEA, 



No. 2. COEBULA PYEIFORMIS, Mcck. 



No. 3. Unio belliplicatus. Meek. 

 No. 4. TiAEA HUMEEOSA, Meek. 



The above-mentioned fossils, and various others brought from this same 

 estuary, or brackish-water formation of Utah, by Colonel Simpson's party, in 

 1860, are all, with perhaps one, or possibly two, exceptions, to be mentioned 

 further on, distinct, not only specifically, but even genericaUy, from those yet 

 known from the whitish or yellowish, coal-bearing, marine sandstones, hold- 

 ing a lower position in the same region. Indeed, the whole group of mol- 

 luscan remains now known from these estuary beds shows clearly that marked 



^ See a paper by Mr. Henry Engelmann and the writer, in Proceed. Acad. Nat. 

 Sci., PMlad., Ap., 1860, p. 126. 



^Ib., December, 1861, p. 440 and 442. 



