bles—which circumstance favors the conjecture that they have been washed out of the overlying beds.

I dug out of the vertical wall of excavation two well-defined implements-one three feet below the surface, the other two feet deeper. Both were imbedded in firmly cemented reddish gravel. The deeper-lying pebble is worn smooth on its chipped edge, the other has the appearance of being rolled but slightly. This section of the old-river shore is half a mile distant from the present bank of the river. I may hereafter refer to it as the Fonticello gravel. Similar beds of gravel on the right bank of the river I have found to contain worked pebbles.

Mr. Mann S. Valentine, to whom I have shown my driftspecimens, has examined a bed of old river-gravel a mile away from the falls, and found some interesting flints. I have not seen them, but do not doubt that they are of the same general character as those contained in the high-level beds on either bank of the river.

In a deep cut of the Petersburg road, a little beyond the High bridge on the south side, I found several flint chips and worked pebbles, which appear to take the staining of the light gray matrix from which they had been taken. The elevation of the terrace at this point is seventy feet above the rapidsthe depth of the specimens below its surface ten feet. My son Charles, who has been trained to look for worked flints, dug out of the clay-bed a rude stone hatchet. An exceedingly beautiful adze or hatchet was found here by me, though not in place. There can be no doubt that it belongs to the same stratum of clay from which other but not similar looking flints were extracted by me. It is shoe-shaped grayish-looking quartzite flint, and has been chiseled into form by a half dozen blows given with a downward stroke. It is not worn. It may have been used either in the hand, or with a haft.

The whitish clay from which I took it lies in a trough of the granite which attains an altitude at this point of sixty feet or more above the level of the river close by. It is capped by the usual brick-earth, which, however, is rather scantily deposited at this place.

It will be understood by the reader that all the discoveries herein mentioned were made in deposits forming parts of the clay and gravel. The implements could not have been introduced into the formations by any other agencies than those which deposited at the same time the containing beds.

Richmond, Va., Jan. 13, 1876.

ART. XXV.-Description of a new Trilobite, Dalmanites dentata; by Dr. S. T. BARRETT.

THE Trilobite described below is from the upper compact beds of the Delthyris shale, a member of the Lower Helderberg formation, near Port Jervis. Orange County, New York. The name, Dalmanites dentata, refers to the dentate margin of the cephalic shield. The following are its characters.

Dalmanites dentata.-Outline of head parabolic; posterior side concave, and posterior angles prolonged into mucronate, slightly falcate extensions; its outer margin throughout dentate. Eyes having about the same position as in D. pleuroptyx, but nearer the outer margins of the cheeks because of the less breadth of the head; number of lenses in a large specimen about 180, eight ranges of them on the highest side. Pygidium triangular, transversely convex; posterior extremity prolonged into a gradually attenuate spine, which is a continuation of the lateral margin, and averages half the length of the axis. Axis sloping evenly throughout, its inferior extremity nearly merged in the border below. Two rows of minute spines extending the entire length of the axis near its center, and scattering minute spines either side over the surface of the segments.

Fragments of what I suppose to be thoracic segments of this species are common. Each terminates laterally in a slender terete spine curved outward and upward at right angles to the rest of the segment; it has a deep narrow longitudinal groove upon its lateral portion, which runs out backward toward the spine, and a deeper transverse groove over its middle portion, the part posterior to which is much larger than that anterior; the surface has minute spines, and otherwise resembles that of the pygidium.

This species has a considerable vertical range, and some layers of the rock are mainly made of its remains. It is associated with Rensselaeria mutabilis, Homalonotus Vanuxemi, Loxonema Fitchiana, Chonetes complanata, and other Lower Helderberg species, kindly identified for me by Professor Hall.

The excellent photograph illustrating this paper was taken, from one of the best of my specimens, by the skillful photographer of Port Jervis, Mr. E. P. Matterson. It is one and a half times larger lineally than the specimen. The writer will furnish those desiring it a second photographic plate, giving a view of the pygidium, eye prominence, and thoracic segment, and has specimens for exchange.

Port Jervis, Dec. 29, 1875.

ART. XXVL—Mineralogical Notes; by EDWARD S. DANA. No. II.- On the Samarskite of Mitchell County, North Carolina.

THROUGH the kindness of Mr. Joseph Willcox of Philadelphia, and of Rev. J. Grier Ralston of Norristown, I have had an opportunity of examining a considerable number of more or less perfectly crystallized specimens of samarskite, which belonged to their cabinets. The results are sufficiently definite to give a pretty exact knowledge of the relations of the species which have been till now very uncertain.

According to information obtained from Mr. Willcox, and also from Professor Bradley, the samarskite is found in the mica mines situated in the mountains of Mitchell County, North Carolina. The rocks of the region are gneiss and mica slate, and the mines are worked in the granite veins which intersect them. Other localities also exist, under similar circumstances, in Yancey, McDougal and Rutherford Counties. The samarskite occurs in masses, generally irregular in shape but sometimes coarsely crystallized, imbedded in a reddish feldspar, which is very much decomposed, sometimes to a kaolin. The masses vary in size, some being very large; one obtained by Mr. Willcox weighed upwards of twenty pounds.

The immediately associated minerals are two other species of the same tantalic group, described further on, and a yellow mica, which may prove upon chemical examination to be of interest.

The samarskite when pure has a deep velvet-black color, though brown by transmitted light on very thin edges. The luster is resinous and very brilliant, and the fracture distinctly conchoidal. The mineral from this locality has already been analyzed by Miss Ellen H. Swallow,* with the following results (specific gravity 5755): Metallic acids, tantalic group, 54.96, SnO2 0·16, UO 9·91, FeO 14·02, MnO 0·91, CeO 5·17, YO 12.84, MgO 0.52, insoluble residue from oxalate of cerium 1-25, ignition 0.66 100-40. The metallic acids were not separated in consequence of the want of material. Attention may also be called here to the analysis, by Dr. Hunt, of the samarskite from Rutherford County, N. C., published in this Journal, II, xiv,

341, 1851.

=

The samarskite exists in all states of purity, being sometimes intimately mixed with the gangue of decomposed feldspar. There are also connected with it several more or less distinct decomposition-products which deserve a chemical examination. A yellow coating over the surface of the masses is very com* Proceedings of the Boston Society of Natural History, vol. xvii, 424, 1875. AM. JOUR. SCI.-THIRD SERIES, VOL. XI, No. 63.—MARCH, 1876.