represent the exact composition of the formation from each neighborhood, since a material difference is often remarked in nodules from the same pit; but these analyses have been chosen from a large number made during the past year, as showing what may be considered the average. It must be stated, however, that the amount of peroxyd of iron, alumina and magnesia given under No. 3, from the Ashley, is higher by a few per cent, than is generally the case in the nodules from that neighborhood. The specimens analyzed were tolerably clean, and more or less air-dry. With regard to the determination of the phosphoric acid, there exists considerable difference of opinion among the chemists who have had the most to do with the analysis of the South Carolina nodular phosphates, each one, it appears, preferring a different method. My experience, as far as it extends, leads me to consider the protochlorid of uranium method as the best for the quantitative determination of phosphoric acid in compounds containing oxyds of iron and considerable alumina. It is true that the results are much lower than those obtained by other methods; but as yet I have found no reason to doubt their accuracy. The organic matter amounts to about one-third to two-thirds of the percentage put down to water of combination and organic matter. Some nodules contain nitrogenous matter sufficient to yield on decomposition with soda lime over per cent of ammonia. (In one specimen 0-26 per cent ammonia was determined). The magnesia rarely exceeds one half per cent.

Artesian water of Charleston, S. C.-The analysis of the water of the artesian well of this city may interest some readers, not only the scientific who may possibly draw important inferences from a knowledge of its composition, since it comes up from below the layer of phosphatic nodules (sixty feet from the surface), but also travellers and health-seekers, who every season drink at this agreeable well, which is also quite popular among our citizens.

The following analysis is the average of several, completed at intervals of a few weeks during last winter and spring. Slight, but unmistakable, changes were noticed in the proportions of some of the ingredients during these investigations. There are two wells, only one, however, is completed. This, the old one, is about 1250 feet deep. The temperature of the water at the spout is 87° F. (or 30.7° C.). Specific gravity (taken at 15° C.), is 1.0015. The amount of solid ingredients in the water = 0.228-0-234 per cent.

In 100 parts solid ingredients:

Bicarbonate of soda....

Chlorid of sodium

52.749

47.051

In 100 imperial gallons (at 15° C.), are contained about one

and a half pounds bicarbonate of soda and one and a quarter pounds common salt.

Charleston, S. C., Jan. 21, 1869.

ART. XXXIV.-Notes on American Fossiliferous Strata; by T. A. CONRAD.

THE discovery of extinct Unionidæ in a clay bank on the New Jersey side of the Delaware river, has directed my attention to the fossil Unionidæ, found by Dr. Hildreth near Marietta, Ohio, described by Dr. Morton in this Journal, in 1836. Comparing specimens from the Delaware with those of Ohio, two species were found to be common to both localities, while a third species, found in West Virginia, near the Ohio river, corresponds to another Delaware species. Again, another Unio from the latter locality, which was presented to me several years ago by Henry C. Lamborne, is found to occur in the bank of the Potomac near Alexandria.

Professor Cope has obtained from the New Jersey clay a portion of a horse's head, which animal undoubtedly lived in the same period with the fresh water shells above mentioned. The question of the geological age of the clay is thus narrowed to more restricted limits, and it must be included in a series from Miocene to Post Pliocene. It has long been a desideratum to discover traces of the rivers and their deposits of the Miocene period of this country. Only one species of fresh water Univalves, and an estuary shell living exclusively in brackish water had noted a trace of a river and estuary, before the fossil shells of the Delaware were found. It seems probable now, that we have evidence of the Delaware in the Miocene period a much broader river than now, and containing a group of Unionida wholly extinct, and very different from the existing group. This ancient bed of the Delaware must have left many traces, but as yet they are not recognized from the great scarcity of fossils except in a mere seam less than a foot in depth. The presence of Anodon in every known locality would seem to imply tide water, ponds or sluggish rivers which became gradually filled up with sediment, and the shells were buried alive, showing no trace whatever of swift flowing or agitated waters. They, however, are all lying on their sides, whereas if the bed of the present river were elevated the Unios would generally be found in a vertical position, as we find the Glycimeris in the

Tertiary of Maryland. This group of extinct freshwater bivalves seems to have been more uniform in character than those of the present day, since it is generally the same on both sides of the Appalachian range, where now the mountains. separate them into two very dissimilar groups, one plain and few in number, and the other numerous, with every variety of form. It is this uniform character, together with the extinction of the shells which lead to the conclusion of their Miocene age. Of the Pliocenes we have no trace along the Atlantic slope, and therefore the geological position must be either that of the Miocene, or of the Post Pliocene, in which latter formation all the species either marine or fresh water are identical with existing forms. The Ohio deposit containing extinct species is thus described by Dr. Hildreth. They are "in a bed of fine micaceous and siliceous sand, the upper part mixed with blue clay." This clay is identical in composition and color with that of the Delaware, containing the same amount of micaceous fragments, showing that both deposits were filled up with similar sediment, and at the same period. The fossils of Ohio are mineralogically the same as those of the Delaware and Potomac, ferruginous casts with portions of the shell remaining. The former are at an elevation of about 600 feet above the latter, which may be due to a rise in the Appalachians. Many naturalists may doubt the Miocene age of this group in consequence of the presence of Equus fraternus Leidy-no solid-ungulate horse having been found in the European Miocene, and because this same species occurs in the vicinity of Charleston in company with the remains of domestic animals. But Dr. Pratt, having studied the geology of that place, found the latter "entombed in direct contact, and in one common burial with the bones and remains of another and older geological period." There is therefore no doubt that the Charleston Equus fraternus lived in the same period with the horse of the Delaware clay.*

CROSSWICKS GROUP.

The lower beds of the eastern Cretaceous are exposed in the sections of the deep cut of the Chesapeake and Delaware Canal, and at Crosswicks, N. J. The group of casts of shells in these beds consists of comparatively small species, nearly all limited to these lower strata, so far as my observation extends. Gryphæa and Exogyra, so abundant in the higher beds of New Jersey, I have not seen in this group.

Prof. Emmons found portions of Equus fraternus Leidy, in a Miocene marl pit, near Elizabeth, Bladen Co., N. C., and other specimens in the Miocene of Pitt Co.

In his report on the geology of New Jersey, Professor Rogers describes a series of clays on the Delaware and Raritan rivers, which he considers the base of the Cretaceous system of the Atlantic slope. By some geologists it is supposed to be the equivalent of the Wealden of Europe, but I think it is of later origin; posterior to the lower greensand, and indicating a continent, which disappeared beneath the cretaceous ocean. These clays seem to be evidences of estuary deposits, as I ascertained by examination of the banks near the village of Washington on South river, a branch of the Raritan, Middlesex Co. These clays rest nearly horizontally and regularly on the undulated and highly inclined surface of gray quartzose sand, replete with ferruginous seams, full of carbonaceous remains of vegetations, too fragmentary to indicate the class of plants from which they have been derived. These seams follow the line of the surface and show the sand to have been disturbed by the movements of the Triassic on which they rest. The lowest stratum of clay is ash colored, in which vast numbers of upright stems of a Neuropteris are seen passing through densely crowded impressions of large leaves, doubtless parts of the same plant. There is evidence of a gentle current in the slightly diverging stems, or it may be of wind acting on the stems above water, but the sediment fell gently on the plants and buried them in clay, which can be traced more than 10 miles at nearly the same elevation above tide. This lower bed is about four feet thick near Washington, and over it is a like thickness of black clay, the upper part full of willow shaped leaves with an entire margin. Över this again is a light colored clay of 20 feet or more in thickness, replete with similar leaves and also vegetable impressions of other kinds.

Mr. Durand informs me that a fragment of one of the leaves from this clay, is that of a fern, the spots on which represent the fructification of the plant. These leaves are abundant in

This Baculite has more distant and much less deeply lobed septa than E. ovatus. I have as yet but a small fragment of this species.