320 G. H. Eldridge — Method of grouping the 



Finally, the practice of the Hay den Survey, in spite of the 

 earlier agreement made by Dr. Hay den with Mr. King at the 

 time of the publication of the Fortieth Parallel maps, gradually 

 inclined to the classification and nomenclature ascribed to Dr. 

 White on a preceding page, so that in the " Geological Atlas of 

 Colorado," the middle Cretaceous groups are distinguished as 

 Colorado and Fox Hills, the former including the Fort Benton 

 and Niobrara, the latter the Fort Pierre and original Fox Hills. 



Turning now to the consideration of the names already in 

 use for the systems of grouping as adopted by former geologists, 

 and, of those proposed in the present article for the general 

 division here advocated, a brief discussion as to their several 

 merits will be the best means of bringing out the relative ad- 

 vantages or disadvantages in their use. 



First, then, in regard to the terms employed by Mr. King in 

 the survey of the 40th Parallel, it is evident that, inasmuch as 

 the method of grouping there adopted cannot longer be accepted 

 in the light of all the facts developed, the significance of the 

 names as there employed must likewise fall to the ground ; and 

 while it is found inadvisable to discard the names used in the 

 reports of this Survey, it is to be understood that they will 

 henceforth have a significance entirely different from that 

 which they ha.ve gained in the usage of Mr. King. 



Dr. White, recognizing the undesirability of changing the 

 nomenclature of groups upon what might be considered too 

 slight a provocation, retained the names of King — " Colorado " 

 and " Fox Hills " — but restricted the former to the two forma- 

 tions, Fort Benton and Niobrara, and designated the general 

 group embracing the Fort Pierre and Fox Hills, by the term, 

 Fox Hills, discarding entirely the old established name of Fort 

 Pierre. This practice Dr. White himself has since suggested, 

 in a personal interview, is for obvious reasons liable to lead to 

 confusion, so well known have become all the terms of the old 

 nomenclature of Messrs. Meek and Hay den. 



The objections to the nomenclature of Powell as given 

 above are at once obvious from the inapplicability of such local, 

 indefinite, and obscure names as " Sulphur Creek " and " Salt 

 Wells " as designations for groups so widely distributed, so ex- 

 tremely characteristic, and now so well known. 



The facts in Canadian geology relative to the lower members 

 of the middle Cretaceous series, which preclude for the pres- 

 ent the grouping together of the formations in Canadian 

 Territory that in a general way may be found to correspond to 

 the Fort Benton and Niobrara in that of the United States, 

 naturally also preclude the use of the term, Colorado, within 

 the same area : for this portion of the Cretaceous, therefore, 

 their formation names already in use, " Fort Benton " and 



