ITS Scientific Intelligence. 



"(3) The marine sandstones and shales immediately underly- 

 ing the Judith River beds do not represent either the Benton, as 

 some Canadian geologists have supposed, or the Fox Hills and 

 upper Pierre, as most geologists of the United States who have 

 examined them have believed, but they constitute a distinct hori- 

 zon within the Montana group which we have called the Claggett 

 formation, from old Fort Claggett at the mouth of Judith River, 

 near which they are well developed. 



" (4) The Eagle formation, from its strati graphic position and 

 faunal relations, marks the base of. the Montana group in this 

 region. 



" (5) The Bearpaw shales, the Judith River beds, the Claggett 

 and the Eagle formations all belong to the Montana group, and 

 together probably form the equivalent of the Pierre as that term 

 is generally understood, though the possibility is recognized that 

 in the typical area the Pierre may have more restricted limits. 



" (6) Faunas similar to that of the Fox Hills sandstone have a 

 great vertical range and are likely to be found at any horizon 

 within the Montana group where a littoral or shallow-water facies 

 is developed. The use of the term Fox Hills as a formation or 

 horizon name outside of the original area in South Dakota is 

 therefore of doubtful propriety, as experience has shown." 



The vertebrate fauna is described by Hatcher. " A considera- 

 ble number of genera and species pertaining to all five of the 

 known classes of vertebrates have been described. Unfortu- 

 nately these genera and species are for the most part based on 

 exceedingly fragmentary and unsatisfactory material." Of fishes 

 there are 8 species ; of tailed Batrachia, 5 ; Plesiosauria, 3 ; Che- 

 Ionia, 14; Rhynchocephalia, 4; Crocodilia, 2; Dinosauria, 3 7 ; 

 birds, 1 ; mammals, 2. " When considered in its entirety, the 

 vertebrate fauna of these beds is remarkably similar to, though 

 distinctly more primitive than, that of the Laramie. Almost or 

 quite all of the Laramie types of vertebrates are present, though, 

 as a rule, they are represented by smaller and more primitive 

 forms. The similarity between this fauna and that of the Lara- 

 mie contrasts strongly with the great dissimilarity between the 

 vertebrates of the Judith River and those of the Atlantosaurus 

 beds, the next older fresh-water horizon in this region." 



Of invertebrates, Stanton notes 35 species of Pelecypods, 30 

 Gastropoda, 1 Placenticeras, and 1 cockroach. " The species 

 enumerated . . . fall into the three general categories of marine, 

 brackish-water, and fresh-water forms, the latter including a few 

 more or less doubtful land shells." The brackish-water fauna 

 contains Ostrea, Mytilus, Modiola, Anomia, Corbicula, Corbula, 

 JPanopcea, Rhytophorus, and Goniobasis. As a rule, the fresh- 

 water forms are found in distinct beds associated with land Mol- 

 lusca and land vertebrates. " It is evident that after the depo- 

 sition of the Claggett formation a considerable area in north 

 central Montana and in Alberta and Assiniboia emerged from the 

 sea and became the habitat of land and fresh-water animals. 



