NATURAL SCIENCES OF PHILADELPHIA 
257 
gy to which we have given little attention,) respecting the fossil leaves onwhic-h 
we mainly based our views in regard to the age of this formation. Consequent- 
ly, we sent outline sketches of a few of them to Professor Oswald Heer,* the 
distinguished authority in fossil botany at Zurich, Switzerland, informing him 
they were from a formation we regarded as Cretaceous and requesting him 
to let us know to what genera and geological epoch he would refer them. 
This letter was sent to Professor Heer in August last, before we Btarted to Kansas, 
and on our return, in the latter part of October, we were disappointed at find- 
ing no reply from him. After waiting some days longer, and receiving no an- 
swer from Professor Heer, we concluded our letter had either failed to reach 
him, or that he was unwilling to express an opinion based upon mere sketches 
of the leaves ; consequently we submitted the whole to Dr. Newbury, who had 
then returned to Washington, and in whose opinion on this subject we have the 
fullest confidence. 
After examining the specimens, Dr. Newbury gave us a written statement 
bearing date Nov. 12, containing a list of the genera to which he had referred 
the leaves, together with some interesting remarks and generalizations, in which 
he expressed the opinion that they are certainly Cretaceous, some of them be- 
longing to genera peculiar to that epoch, and that the whole belong to more 
highly organized plants than anything known in the Triassic or Jurassic flora. 
Knowing as we did that the rocks from which these plants were obtained, 
— beyond all doubt, — hold a position beneath, at least, eight hundred feet of 
Cretaceous strata, containing great numbers of Ammonites, Scaphites, Baculiies, «f-c., 
it of course never once occurred to us that any person might suppose it 
Tertiary. 
About the thirteenth of November we sent on to the American Journal of 
Science, a communication containing Dr. Newbury's list of the genera to which 
he had referred our plants, with some extracts from his remarlcs, all of which 
will appear 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 ws 
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 (Credneria,) 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, en- 
titled " Letters on some points of the Geology of Texas, New llexico, Kansas and 
Nebraska; addressed to Messrs. F. B. Meek and F. V. Hayden, by Jules Marcou." 
In this pamphlet Professor Marcou quotes Professor Heer's conclusions in re- 
gard 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 belonging to each of these two widely different geological epochs. 
Having a very high regard for Professor Heer's opinions on any question in 
fossil botany, where he has had an opportunity to examine the specimens them- 
selves, or to study good figures and descriptions, we are quite sure, had the 
whole collection been submitted to him, instead of mere sketches of a few of 
the species, his opinion would have been very dilferent. At any rate, we can 
assert with the fullest confidence that it is absolutely impossible that this forma- 
tion, 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 inference drawn from having seen this formation under cir- 
* Our friend Dr. Newberry was then in INew Mexico. 
t For dftscriptions of theee plants by Prof. Ileer, see the last two pages of this paper. 
1858.] 
