iNTi;oi>r< Tory remarks, xxvii 



with a few that may possibly lie brackish-water types, all belonging to 

 distinct species from those found in this rock on the Missouri. The identity 

 of these beds at the two localities mentioned, however, is shown by the 

 occurrence in them, in both districts, of some of the same species of fossil 

 leaves mentioned farther on, as well as by many intermediate outcrops. The 

 fossils from this rock are figured on our plates 1 and 2. 



Although this formation was, as already shown, from the first included 

 by us in the Cretaceous, this conclusion was for a long time disputed; Pro- 

 fessor Marcou having at one time inferred it to the Trias, and later to the 

 Jurassic, in which former opinion some American writers were inclined to 

 concur. 



In 1858, Dr. Hayden discovered in these beds on the Missouri numerous 

 well-preserved impressions of leaves of the higher types of dicotyledonous 

 trees, such as Liriodendron, Populus. Platanus, Sassafras, etc.; and, although 

 neither of us had ever given much attention to the study of fossil botany, a very 

 limited knowledge of that subject was sufficient to convince any one that a rock 

 containing the remains of such a flora, according to all experience, could not be 

 as old as Jurassic ; while its position beneath well-marked Cretaceous strata, in 

 an undisturbed district, was even more conclusive evidence that it could not be 

 Tertiary. In order, however, to remove all doubts on these points from the 

 minds of others, sketches of some of these leaves were drawn by the writer, 

 and sent to Professor Heer, of Ziirich, well known as an eminent authority 

 on botanical palaeontology. Much to our surprise, however, a communication 

 some time after received from him informed us that he thought, from the 

 affinities of these leaves, that they were of Miocene age; which opinion was 

 also expressed by him in a printed paper sent at the same time. Professor 

 Marcou, who was at the time at Zurich, likewise published a paper adopting 

 Professor Heer's opinion, and stating that he believed that our Cretaceous 

 division No. 1 included all sorts of formations excepting Cretaceous. 



Before receiving Professor Heer's reply, however, we had submitted the 

 specimens of these leaves to Prof. J. S. Newberry, and he had fully concurred 

 with us in the opinion that the beds from which they came are of Creta- 

 ceous age. 



For a long time, however, our conclusions on this point were questioned, 

 particularly in Europe, where Professor Heer's opinion naturally carries much 

 weight. Nevertheless, when, some years after, Professor Marcou and Pro- 



