26 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



slated, ill Uic first i)lacc, ilial Emmons evidently regarded it as Cretaceous, as 

 may be seen from liis remarks in Jlr. King's report, ])id)!islied in 1870, wliile 

 Dr. llaydcn favored liie conclusion iliat it is a marine Tertiary group, or a 

 tnnisilion series between tlie Tertiary and the Cretaceous, in his reports of 

 thill and the following year." 



"Tin; only fossils I had ever seen from this formation previous to visiting 

 the region during the jiast summer were two species of Ostrea and one of 

 Anomia from Point of Rocks, and two shells, one or possibly both rtilated to 

 Corbicula, from llallvillc. Tliose from Point of Rocks I referred to the Creta- 

 ceous, placing them in the Cretaceous list in Dr. Ilayden's report, 1871. 

 This 1 did mainly because there were among them no fresh-water or strictly 

 brackish-water types, while up to this lime we knew of no Tertiary of ex- 

 clusively marine origin in all this internal region of the continent. I was 

 also in pari influenced in making this reference by the similarity of one of 

 the Oysters to a Cretaceous species found in California, wiiile the Anomia 

 likewise closely resembled a IVxas Cretaceous shell described by Roemer 

 under the name of Ostrea anomio'formis, which certainly seems not to be a 

 true Oyster. The two shells from TTallville, however, I referred to the Eo- 

 cene, not only because they were closely allied to Eocene brackish-water 

 forms from the Paris Basin (peculiar depressed and elongated form of Cor- 

 bicula), but because I was not aware at the time that the llallville mines 

 occur in the same formation as the Point of Rocks beds, nor even within 

 fifty to seventy-five miles of the same locality. 



"On visiting these localities, however, last summer, I was somewhat sur- 

 prised to find thai tlie llallville mines are only some seven or eight miles from 

 Point oi' Ivocks, and belong to liu^ same geological formation. A careful 

 examination, also, soon rendered it evident that all of the rocks for sixteen 

 hundred to eighteen hundred feet or more above the Hallville coal beds, up 

 to and including the stratum in which we found the large reptilian remains 

 at Black Butles, and for even a little greater thickness below the Hallville 

 horizon, certainly belong to the same group or series of strata, and that fresh- 

 and brackish- water types of fossils occur along with salt-water forms at all 

 horizons wherever we found any organic remains thronghout this whole 

 series." 



I'^roni this f:icl. Prof ]\Icek was induced to modify his views, and to con- 

 sider the whole series Cretaceous, by some reason which 1 do not consider as 



