436 GEOLOGICAL SURVEY OF THE TERRITORIES. 



foruia, referred to tlie Cretaceous. A Modlola from the same horizon, also, appears to 

 be specilically ideutical with M. rcdcniaUx, of Roemer, from the Cretaceous of Texas. 

 Dr. llaydeu also has, from a litth' above the coal-beds at Coalville, specimens of Ostrea, 

 that seem nmch like O. Idriaensis aud O. Ilrciveri, of Gabl), from the upper beds of the 

 California C!retaceous. As no other fossils were found directly associated with these 

 oysters, however, uor any marine forms above them, it is possible that they may be- 

 long to the Lower Tertiary. 



From the allinitic's of some of these fossils to forms found in the latest of the beds 

 referred in California to the Cretaceous, and the intimate relations of these marine 

 coal-bearing strata of Utah to the oldest Tertiary of the same region, and the apparent 

 occui'rence of equivalent beds bearing the srme relations to the oldest brackish-water 

 Tertiary beds at the mouth of JnditL Rivc^r on the Upper Missouri, I am inclined to 

 believe that these Coalville beds occupy a higher horizon in the Cretaceous than even 

 the Fox Hills beds of the Upper Missouri Cretaceous series ; or, in other words, that 

 they belong lo the doaUifj or latent member of the Cretacenua. 



These remarks certainly ought to make it clear enougli, one woiild 

 think, that I regarded the coal-bearing strata at Coalville, Utah, dud 

 near the mouth of Sulphur Creek, on Bear Eiver, Wyoming, as being 

 of Cretaceous age.* A few i)ages further on in the same report, I gave 

 a list of all the fossils collected during the preceding summer by Dr. 

 Hayden's party, that I referred to the Cretaceous epoch. In this list, it 

 will be seen, I placed all of tlie few fossils in the collections then under 

 consideration, from the coal series at Coalville, Utah, and Bear Eiver. 



In making out the Cretaceous list mentioned above, I endeavored to 

 express, by a number opposite the name of each species, the particular 

 horizon in the Cretaceous series of the Upper Missouri, to which the 

 bed that contained it belongs. This I fully explained on page 289 of 

 the same report cited, as follows : " The numbers 1, 2, 3, 4, and 5, along 

 the right-hand margin of the list,t opposite the localities, show to which 

 member of the Upper Missouri Cretaceous each s[)ecies belongs, the 

 subdivisions of the Upper Missouri Cretaceous having been severally 

 named and numbered from below upward, as follows: No. 1, Dakota 

 group; No. 2, Fort Benton group; No. 3, Niobrara division ;' No. 4, 

 Fort Pierre group ; and No. 5, Fox Hills beds; the names being derived 

 from localities where the several formations are well develoi)ed." 



In accordance with this plan, I assigned each species in the list to its 

 proper horizon in the Cretaceous series, by adding after the localit}', 

 " Cret. No. 1," " Cret. No. 2," &c., according to its position, except- 

 ing those from Coalville. These I could not refer to their precise 

 horizon in the Cretaceous, because, although not doubting that they 

 belong to the Cretaceous system, I was, as already explained, in doubt 

 whether the beds in which they were found correspond exactly to any 

 of the recognized subdivisions of the Upper Missouri series, being, as 

 stated, rather inclined to think they form the closing member or divis- 

 ion ot the Cretaceous, holding a position above the horizon of No. 5 of 

 the Upper Missouri section. Consequently, in order to give expression 

 to this doubt, as well as to follow out the system of notation, I placed 

 opposite each of the species from Coalville, and the coal-bearing sand- 

 stones at Bear Eiver, the words " Cret. No. ? " meaning thereby, 

 of course, that I was in doubt whether these beds corresponded exactly 

 with any particular one of the recognized subdivisions of the Upper 

 Missouri series ; which, it should be remembered, only represents a part 

 of the whole Cretaceous system. 



* Another quite distinct formation at the. Bear River locality, containing a jieculiar 

 group of fresh and brackish water types of fossils, all entirely diflerent from forms 

 found in the nuuiue beds containing the valuable beds of coal there, was referred by 

 me provisi<mally toth(! lower Eocene. 



t These numbeis were placed on the right-hand margin of the list in the MS., but 

 are not exactly so in the list as ])rinted. 



