8 AMERICAN GEOLOGY. mt, chert, in order to arrive at such a conclusion. If true, this would be unique in the Cretaceous rocks, where a fossil never has been found to range from the base to the summit of the formation in the same country. Sixth.—Morton says in his Synopsis that the original spe cimens of his G. Pitcheri were picked up on the plains of the Kiamesha, and at the falls of Verdegris river, by Dr. Pitcher; so far as I know, no other Geologist has ever visited these two localities, and I think a fair way of settling for ever the question of the identity of the Pyramid Mount fossils with spe cies found at Fort Washita, the plains of the Kiamesha, and Ver degris river, would be for a Geologist to visit these different localities and collect carefully all the fossils he can find. My original specimens figured in the Bulletin de la Soc. Geol. de France and in my Geology of North America, are deposited in the Museum of the Geological Society of London and can be always easily consulted. For my part, 1 hope such a Geo logist will be found before long, and I am too much a friend to the truth not to submit at once to the result of such a comparison. Seventh. — It is almost needless to say that I consider the Jurassic rocks of Pyramid Mount as of the same age with those of the Black Hills, and not far beneath them as you think. Eighth. — In.your letter of the 22th August 1858 you say: «You were certainly mistaken in supposing we had identified «the Trias in Nebraska; we are not however disposed to take «offence at the form of your note in the Bibliolheque Vni- « verselle, as our remarks in the Intelligencer were too brief to «be fully understood by you. Dr. Hayden merely sent them «to you because he thought it would be gratifying to you to «know we had found reliable paleontological evidence of the «existence of Jurassic and Permian rocks in Nebraska and «Kansas.)) Perhaps I am mistaken; but I think in the incom plete section given by Hayden in the second edition of his memoir entitled: Explanations of a second editioti of a Geolo-