Cretaceous genus (Credneria,) the nervation being obscure, and the others 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 Geology of Texas, New Mexico, 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 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 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 themselves, 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 different. At any rate we can assert, with the fullest confidence, that 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 inference 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 localities.

In order to satisfy others that we are not mistaken in this, we will give a few of the many 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 longitude 97° 30' west. Here we found it forming the upper part of several isolated elevations known as the "Smoky Hills," at an altitude of about 1200 feet above the Missouri at Fort Leavenworth. At this locality, however, we saw no rocks overlying it, and consequently have no stratigraphical evidence that it is the same rock seen by us at other localities under Cretaceous beds; but our lithological and paleontological evidence is quite conclusive on this point, for this rock in color, composition, and all other respects, is undistinguishable from No. 1, of the Nebraska section, as seen near the mouth of Big Sioux river on the Missouri, and contains numerous fossil leaves, some of which are identical with those occurring in No. 1, at the last

SECOND SERIES, VOL. XXVII, No. 30.-—MARCH, 1859.

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1.

mentioned localities. Amongst these leaves Dr. Newberry has also identified at least one genus (Ettingshausinia, No. 3 of the following cuts,) peculiar to the Cretaceous System. The specimens from which this outline was drawn, was not in our possession at the time we sent the outlines to Professor Heer, but was afterwards found associated with several of the species from which the sketches sent him were drawn. The annexed cuts, Nos. 1 and 2, represent other forms from the same rock.

Bearing in mind that all the rocks here have a gentle but uniform inclination or dip to the northwest; and that the formation under consideration con

sists of red, yellowish, and other colored sandstones and clays, with generally more or less impure lignite and ferruginous concretions, we will be prepared to recognize it at lower and lower elevations as we proceed northward.

3.

Without undertaking to mention in detail all the intermediate places where this rock is known to occur, we pass at once to focalities where it has been observed by various persons beneath Cretaceous beds. First at several points on the Republican fork of Kansas river, about eighty miles above its mouth, and some sixty miles nearly due north of the Smoky Hills, it was seen by Dr. H. Englemann at an elevation of about 1000 feet above the Missouri, at Fort Leavenworth. Here Dr. Englemann describes it as "a coarse grained, friable dark brown ferruginous sandstone, and very compact white and light colored shaly sandstone."

Near this locality he saw it overlaid by Cretaceous beds, the section given by him being as follows descending. "The top was formed of a white granular limestone, and another more impure yellowish variety full of Inoceramus. Below there seemed to be a sandy clay, probably from decomposition of arenaceous and argillaceous slates, and then a stratum of gray compact subcrystalline limestone in thin layers, full of Inoceramus Cripsi.

In the lower part of the hill the ferruginous sandstone was exposed." Report Sec'y War, Dec. 5, 1857, p. 497.

Again it has been seen by several observers at different times near Little Blue river, not far from the Kansas and Nebraska line,-lat. 40° and a little west of the 97° of west longitude. Here at an elevation of about 700 feet above the Missouri at Leavenworth, or three hundred feet below the horizon of the localities on Republican fork, and, five hundred feet below the elevation of the outcrops seen by us on the summits of the Smoky Hills, our deceased friend, Mr. Henry Pratthen, saw near Wyeth's creek, in 1853, the following exposures in descending order:

1. Slope, height not given.

2. Yellow and whitish limestone filled with casts

of Inoceramus, referred by him to I. myteloides No. 3, Nebraska Sec. I. problematicus.

3. Slope, thickness not given.

4. Red ferruginous sandstone with leaves of dicotyledonous tress.

No. 2, Nebraska Sec.

No. 1, Nebraska Sec.

A short distance west of this exposure Dr. J. G. Cooper informs us he saw outcrops of a red sandstone in the valleys at about the same elevation; and above this, exposures of dark gray laminated clay answering exactly to the description of No. 2, of the Nebraska section, while above the latter, near the tops of the hills, he met with outcrops of light colored limestone containing numerous casts of Inoceramus.

At other localities not far to the southwest of the foregoing, Mr. Hawn saw exposures of light colored limestone forty-five feet in thickness, containing great numbers of Inoceramus which we referred, from specimens sent by him, to I. problematicus.* Below this there was a slope of twenty-seven feet in which he saw no exposures, while still lower he observed outcrops of dark ferrugi nous and yellow sandstone, and various colored clays with impressions of leaves, resembling, as he supposed, those of oaks and willows. (See his section published by us in the Proceedings of the Academy of Natural Sciences o' Philadelphia, May, 1857.)

Proceeding northward from the last mentioned localities, we find on reaching the Loup fork of Platte river, near the eastern limits of the Pawnee reservation, outcrops of the light colored Inoceramus beds already mentioned, (No. 3, Nebraska section,) near the water's edge; and at the mouth of Loup fork, on the

We have referred this species to I. problematicus with some doubt; it is the same species inscribed by Dr. Schiel in the second volume of the Pacific Rail Road Report, page 108, plate 3, figure 8. It is rather longer on the hinge than is common in I. problematicus, from which it may be distinct. We always refer to this shell in speaking of I. problematicus, in this paper.

Platte, the red sandstone No. 1, so often referred to, crops out near the river margin, while the Inoceramus beds are seen in the bluffs above it. Going down the Platte in a direction nearly contrary to the dip of the strata, we find this sandstone rising up so as to form near the mouth of Elk Horn river, bluffs some sixty feet in height. Here it seems to rest directly upon upper Carboniferous rocks. Continuing on down the Platte, we find this red and yellow sandstone rising higher and higher in the hills until we come within five or six miles of the Missouri, where it is seen with its base elevated near sixty feet above the Platte; and there are probably outliers of it between that point and the Missouri at greater elevations. So that we find the same formation which at the Smoky Hills, is elevated twelve hundred feet,

on the Republican river, one thousand feet,-and near Little Blue river seven hundred feet, above the Missouri at Leavenworth, has by the gradual northwestern dip of the strata, sunk to within about one hundred feet of the Missouri at the mouth of the Platte.*

Ascending the Missouri from the localities just mentioned, we see occasional exposures of the upper Carboniferous rocks, which gradually sink lower and lower until they pass beneath the river near Florence, to be succeeded by the reddish and yellow sandstones, &c., of No. 1.-(Nebraska section.) At localities along the river above this, occasional exposures of this formation are seen with its characteristic fossil leaves; and at several points, some thirty miles below the mouth of Big Sioux river, it forms perpendicular escarpments of yellowish sandstone rising from the water's edge to an elevation of about eighty feet; while at higher points, back on the summits of the hills, the same calcareous beds are seen, containing Inoceramus problematicus. Here at a quarry in the sandstone (formation No. 1,) some twenty feet above the level of the river, one of us (Dr. H.) collected a large number of fossil leaves, some of which are identical with species found by us in this rock at the Smoky Hill locality already mentioned. The sketches of leaves sent by us to Prof. Heer were mostly drawn from specimens collected at this locality.

At the mouth of Big Sioux river a low bluff of this formation, not more than fifteen or twenty feet in height, is seen, and on the hills back a little from the river, at a higher elevation, the same Inoceramus bed crops out at several places, and is used for

* The gradual descent of the Missouri river makes its surface at Fort Leavenworth, about three hundred feet lower than at the mouth of the Platte, hence the exposures of No. 1, seen at the latter locality, near one hundred feet above the Missouri, are some four hundred feet above the level of the Missouri at Fort Leavenworth, and of course about three hundred feet lower than the Little Blue river outcrops. The dip however, is greater than this would indicate, for the strata incline towards the northwest, while the mouth of Platte river, is northeast of the Blue river localities.