320 GEOLOGY AND MINERALOGY. 



to genera peculiar to that epoch, and that the whole belong to more highly or- 

 ganized plants than anything known in the Triassie or Jurassic flora. 



Knowino- as we did that the rocks from which these plants were obtained — be- 

 yond all doubt, — hold a position beneath, at least, eight hundred feet of Cretaceous 

 strata containing great numbers of Ammonites, Scaphites, Baculites, &c., it of 

 course never once oecured to us that any person might suppose it Tertiary. 



About the thirteenth of November we sent to the American Journal of 

 Science, a communication containing Dr. Newberry's list of the genera to which 

 he had referred our plants, with some extracts from his remarks, all of which have 

 appeared in the January number of that Journal. Some two or three weeks after 

 •we had corrected the last proof of this paper, we received (13th of Dec.) a letter 

 from Professor Heer, bearing date of Nov. 20, in which he informed us that our 

 letter had reached him at a late date, in consequence of his absence from home, 

 and that after his return, other engagements had prevented him from replying 

 sooner. In this letter Professor Heer, in accordance with our request, sent us a 

 list of the genera, as near as it was possible for him to make them out from hastily 

 drawn sketches, and also kindly furnished brief diagnoses of the species, stating at 

 the same time that although one of the outlines resembles a Cretaceous genus 

 (Oredneria,) the nervation being obscure, and the others being more like Tertiary 

 forms than anything known in the Cretaceous of the old world, he was inclined to 

 the opinion that they are Tertiary, 



Along with Professor Heer's letter, we also received a printed pamphlet entitled 

 " Letters on some points of the Oeology of Texas, New Mexico, Kansas and Nebras- 

 ka ; addressed to Messrs. F. B. Meek and F. V. Hayden, by Jules Marcou." In 

 this pamphlet Professor Marcou quotes Professor Heer's conclusions in regard to 

 our fossil plants, and expresses the opinion that No. 1, of the Nebraska section, is 

 both Miocene and Jurassic, or in other words, that we have included in it strata be- 

 longing to each of these two widely different geological epochs. 



Having a very high regard for Professor Heer's opinions on any question in fos- 

 sil botany, where he has had an opportunity to examine the specimens themselves, 

 or to study good figures and descriptions, we are quite sure, had the whole col- 

 lection been submitted to him, instead of mere sketches of a few of the species, 

 his opinion would have been very different. At any rate, we can assert with the 

 fullest confidence it is absolutely impossible that this formation, or any part of it, 

 can be Tertiary, for we know it passes, as already stated, beneath at least eight 

 hundred feet of Cretaceous strata. This is not mere conjecture, nor an infereuce 

 drawn from having seen this formation under circumstances leading us to suppose 

 from the dip of the strata, that it must pass beneath the Cretaceous if continued in 

 a given direction at the same angle of inclination, but from the fact that it has 

 actually been seen, directly beneath the other Cretaceous rocks, not merely at 

 one place, and by one observer, but by several persons at numerous locali- 

 ties. 



In order to satisfy others we are not mistaken in this, we will give a few of the 

 manv facts in our possession, bearing on this question. In the first place, we 

 would remark that the farthest point towards the south at which we have seen 

 this formation, is near Smoky Hill river, in Kansas, latitude 38° 30' north, and 



