In the specimen above figured there is an aperture in the beak, but in another there is no appearance whatever of a perforation. This genus resembles Acrotreta, but differs therefrom in having a large convex deltidium. It seems to be also closely allied to Kutorgina. The shell which I have described under the name of Obolus Labradoricus belongs to this genus.

I. bella was found by T. G. Weston, in a boulder of limestone associated with numerous fragmentary trilobites, of primordial age, near Trois Pistoles below Quebec. A closely allied species of the same genus occurs in the primordial limestone at Topsail Head, Conception Bay, Newfoundland.

FOSSILS IN THE HURONIAN ROCKS.

ASPIDELLA TERRANOVICA, nov. gen. and spec.

FIG 14 Aspidella terranovica, two specimens on a small slab of stone, slightly restored,

These are small ovate fossils five or six lines in length and about one-fourth less in width. They have a narrow ring-like border, within which there is a concave space all round. In the middle there is a longitudinal roof-like ridge, from which radiate a number of grooves to the border. The general aspect is that of a small Chiton or Patella, flattered by pressure. It is not probable, however, that they are allied to either of these genera.

Associated with these are numerous specimens of what appear to be Arenicolites spiralis, a fossil that occurs in a formation lying below the primordial rocks in Sweden. These fossils were first discovered by A. Murray, Esq., F.G.S., in 1866. Other specimens were collected by Capt. Kerr, R.N., Mr. Howley and Mr. Robertson.

They occur near St. Johns, in the Huronian. A more detailed description will be given hereafter.

STENOTHECA PAUPER, spec. nov.

Description.-Shell small, conical, with the apex incurved, laterally compressed. Aperture ovate, elongated in the plane in which the curvature of the apex occurs. Surface with four or five small engirdling convex ridges. Length of aperture about 1 lines; width about 1 line; height of shell about 1 line. Occurs in the red limestone at Bridgus, Conception Bay. In the Quar. Jour. Geol. Soc. of May last, Mr. Hicks has described and figured, under the name of Stenotheca cornucopia, a small shell which is evidently congeneric with this. To the same genus should perhaps be referred the shell known as Metoptoma rugosa of the Lower Potsdam ? of New York.

SCENELLA RETICULATA, gen. and spec. nov.

Description.-Shell small, almost uniformly depressed, conical; apex central or nearly so; an obscure carina extending from the apex down one side to the margin. Aperture nearly circular, apex very slightly incurved towards the side opposite the carina. Surface reticulated with fine radiating and engirdling striæ, just visible to the naked eye. Diameter of the aperture of the largest specimen collected, 3 lines; height of the apex, 2 lines.

Occurs at Topsail Head, Conception Bay.

Species resembling this have been heretofore referred to Capulus, Metoptoma, &c., to which, however, they do not belong. For the present I propose to refer those with a strongly corrugated surface to Stenotheca, and the others with a smoother surface to Scenella.

(To be Continued.)

WHAT IS TRUE TACONIC ?

BY PROF. JAMES D. DANA.

The true use of the term Taconic should be learned from Prof. Emmons's first application of it when he made his formal announcement of the "Taconic system." In his final New York Geological Report, 4to., 1842, the rocks so-called are those of the Taconic mountains, on the borders of Massachusetts and New York, together with the quartzite, limestone, and slates adjoining on the east, and not the slates far west of these mountains; †

• Professor Emmons opens the subject of the "Taconic System" in his final Report (1842) by saying that it extends north through Vermont to Quebec, and south into Connecticut; but the only rocks he describes as the rocks of the system are those of Berkshire County,

moreover the slates, the rocks of the mountain, were the typical beds, and not the quartzite. Hence, if there are any Taconic schists or slates, those of the Taconic range are the rocks entitled to bear the name, being Taconic geographically, and Taconic by the earliest authoritative use, Prof. Emmons the authority.

Prof. Emmons, in his Agricultural Report, subsequently published (in 1843), announced the Primordial beds of Bald Mt. (near Canaan Four Corners, in Columbia Co. N. Y.), as Taconic also; but this did not make them so. He referred to the Taconic the Black slates of northern Vermont, since shown to contain primordial fossils; he searched the country north and south for other Taconic rocks, and found them as he thought; and he set others on the search, not only in this country, but over the world. But all this has not changed the fact that the true Taconic beds, if any are such, are those he first so announced; and that the rest, so far as they are of different age from these, younger or older, have been dragged into the association without reason. The Taconic rocks of Berkshire and of the counties of New York just west, always bore the most prominent part in his later descriptions of the Taconic system.

The error on the part of Prof. Emmons, in referring beds of other ages to the Taconic system, is not surprising, considering the difficulties in the case. But it was no less an error; and his name as a backer cannot make the wrong right.

Geologists now regard the slates of Taconic Mt. and the limestone, also, as of Lower Silurian age, but later than the Potsdam sandstone. Logan refers them to the Quebec group. Whatever the period of the slates, or slates and associated limestones, to that period properly pertains the term Taconic.-Amer. Naturalist.

Massachusetts, and their continuation westward into New York. These are the typical rocks on which the system was founded. On plate xi, four figures representing sections across this particular region are given. The only Vermont observations are contained in the only other section on the same plate represénting a section from Lake Champlain to Richmond, Vt., through Charlotte. No description of the rocks of this section is to be found in the text of the volume.

In figure 4 of plate xi. (referred to in the preceding note) representing a section through Graylock, the "Taconic slate" stops just west of Berlin, Rensselaer County, New York, the slates on the west being put down as "Hudson River shales," and in figs. 2 and 3, the boundary is near Petersburg, north of Berlin. The extension of the Taconic to the Hudson River appears first in Prof. Emmons' Agricultural Report, published in 1843.