Hatcher : Thf^ Jurassic Dinos.mr Dki'osits. 341 



preserved can hardly be doubted, indeed we may I)e quite jiositive 

 that every fresh water or xolian deposit of whatever age has its marine 

 equivalent, and the writer sees no reason why the lower members of 

 the dinosaur beds of Garden Park, should not be the equivalents of the 

 marine Baptonodon beds farther north, while the upper dinosaur beds 

 of the same region and the entire series of dinosaur beds farther north 

 would become the equivalents of the marine Lower Cretaceous. That 

 the lowermost dinosaur beds of Garden Park are of an earlier age than 

 those of Como Bluff in southern Wyoming and Piedmont, South 

 Dakota, as well as of the other localities lying to the north, will I 

 think be clearly demonstrated when we come to make a comparative 

 study of the dinosaur remains from each. From the foregoing re- 

 marks it will readily appear that in the Garden Park region the 

 problem of separating the Jura from the Cretaceous becomes a diffi- 

 cult one, the top of the Dakota becomes the natural dividing line, 

 whether considered lithologically or paleontologically, and I have no 

 doubt that these difficulties will be further enhanced by the discovery 

 of dinosaur horizons throughout the entire upper series of sandstones 

 and shales which we now consider as belonging to the Dakota. This 

 is almost sure to follow as a reward for a patient and careful search 

 in these beds, and will be most welcome as adding one more link in 

 connecting the long gap which at present exists between Jurassic and 

 Laramie dinosaurs. Of the history of American dinosaurs from the 

 close of the Jura to the beginning of the Laramie we at present know 

 nothing, save C/aosai/rus agiiis Marsh from the Niobrara of Kansas 

 and a few remains, for the most part quite fragmentary, described by 

 Leidy, Cope, and Marsh, from the Cretaceous marls of New Jersey 

 and North Carolina. 



