4 AMERICAN GEOLOGY. liman's Journal, were not so absurd after all, and I gave to the article published in the Bibliothe'que Universelle de Gendve, Juin 1858 (Notes pour servir d une description giologique des Montagues Iiocheuses) a direction showing that change in your opinions, be lieving candidly that such was the meaning of your message. From subsequent letters it appears this was not the case, and now it is my duty to give a few words of explanation, that no mistake may arise from what has occurred. In your letter dated Washington May 30th 1858 you say: «I hope you will permit me respectfully to suggest, that I cannot « agree with you in your conclusions respecting the Pyramid Mount « section (see: Geology of North America, p. 18). By this I mean to « say, that I regard all the beds of that section down at least to A. «as Cretaceous. The beds below may be Jurassic or Triassic, «though I know of no evidence that they are so. Notwithstanding «the high authorities you have for regarding the Gryphcea and « Oslrea found at Pyramid Mount as G. dilalata and 0. Marshii, a I feel quite confident from collections shown to me from the «South West, that these fossils are at some places associated «with well marked Cretaceous forms; while numerous facts « point to the conclusion that the bed from which you obtained «these fossils at Pyramid Mount, is equivalent to N° 2 of our «Nebraska section, in which we find Baculites and other Cre taceous fossils. In addition to this, all the facts in our pos- « session respecting the rocks in Kansas and south to the Ar- «kansas river, point directly to the conclusion that the sand- « stones of our N° 1 in Nebraska, in which the leaves already ((mentioned occur, are represented by the beds B., C., and «D. of your Pyramid Mount section; while the beds from which «Dr. Hayden obtained the Jurassic fossils near the Black Hills « hold a position far beneath these. » I respect your opinion, gentlemen, but I beg you to allow me to continue to regard my observations and conclusions as exact. I would also say that I do not understand the value of the following phrase in a note to your memoir entitled: Descrip tions of New organic remains, collected in Nebraska Territory