to earlier and latet Formations. . 435 



Missouri Cretaceous, and as underlying strata which bear mol- 

 luscan forms such as characterize the Pierre and Fox Hills 

 groups of the same section. 



The fossils which they report as coming from the Belly 

 River formation are wholly different from those that charac- 

 terize the formations which underlie it, as well as the one 

 which immediately overlies it. Their collections not only in- 

 dicate the absence of true marine forms from the Belly River 

 formation, and the presence in it of remains of both verte- 

 brate* and invertebratef faunas which are similar to those of 

 the Laramie, but they contain a considerable number of mol- 

 luscan forms which are specifically identical with a part of 

 those which characterize the Laramie Group. 



Those geologists furthermore rej)ort that the marine Creta- 

 ceous strata which overlie the Belly River formation are, in 

 turn overlaid by true Laramie strata, bearing the characteristic 

 fossils of that formation. The following table shows the rela- 

 tion of the forementioned formations, with one another ; and 

 also the relation of Dr. Dawson's section with the Upper Mis- 

 souri section of Meek & Hay den. 



Meek and Hayden. Dawson 4 



Judith Riverbeds [Laramie] .Laramie. 



No. 5. Fox Hills Group ) -p ttm, -, td- q 



at . ^ >. o- r\ \ * ox Hills and Pierre.© 



.No. 4. J^ort Fierre Group \ s 



Wanting Belly River beds. 



No. 3. Niobrara Group ) ^ . -, /7sT . , x 



AT n tp. r> , ^ L y Benton and (Niobrara)? 



No. 2. hi. Benton Group ) v ' 



No. 1. Dakota Group Dakota; 



and upper part of Kootanie. 



Considerable paleontological difference between the com- 

 bined Benton and Niobrara groups beneath, and the Pierre 

 and Fox Hills groups above, has long been known to exist. In 

 recognition of this difference Meek designated the two divis- 

 ions respectively, as the " upper " and " lower series " ; and as 

 "Earlier and Later Cretaceous." Still, those formations have 

 been generally regarded by geologists as forming a continuous 

 series of marine deposits which was unbroken as such until the 



* Professor E. D. Cope has examined collections of vertebrate remains from 

 the Belly River formations, and has personally informed me that they consist 

 wholly of Laramie types. 



f See Cont. Canadian Paleontology, vol. i, Part I, pp. 55-77; and plates IX 

 and X. 



% See Ann. Rep. Geol. and Nat. Hist. Surv. Canada for 1885, p. 166, B. 



§ It will be seen that Dr. Dawson combines together the Pox Hills and Pierre, 

 and also the Benton and Xiobrara divisions, recognizing only a single formation 

 in each of the two cases. This combination has also long been adopted by mem- 

 bers of the U. S. G-eological Survey, on the ground that there is no sufficient rea- 

 son for separating them except for occasional local study. 



