This species has been found at Bic and St. Simon. Fig. 1, b, representing the transverse section, is not so distinctly flattened on the ventral side as it is in most specimens. Collected by T. C. Weston. H. AMERICANUS.-Length from twelve to eighteen lines, tapering at the rate of about four lines to the inch. Section triangular, the three sides flat, slightly convex or slightly concave, the dorsal and lateral edges either quite sharp or acutely rounded. Lower lip rounded, projecting about two lines in fullgrown individuals. Surface finely striated, the striæ curving forwards on the ventral sides, and passing upwards on the sides at nearly a right angle, curve slightly backwards on the dorsum. In a specimen eighteen lines in length, the width of the aperture is about six lines and the depth about four, the proportions being slightly variable. The operculum has a very well-defined conical ventral limb, the apex of which is situated above the centre, or nearer the dorsal than the ventral side. The dorsal limb forms a flat margin, and is so situated that when the operculum is in place, the plane of this flat border must be nearly at right angles to the longitudinal axis of the shell. In an operculum six lines wide, the height of the lower limb to the apex of the cone, is two and a-half lines, and the width of the flat border, which constitutes the dorsal limb, about one line. This species occurs at Bie and St. Simon; also at Troy, N.Y., where it has been found abundantly by Mr. S. W. Ford of that city. It is Theca triangularis of Hall, Pal. N.Y., vol. I., p. 213, 1847. As that name was preoccupied by a species previously described by Col. Portlock, Geol. Rep. on Londonderry, p. 375, pl. 28 A, fig. 3a, 3b, 3c, 1843, it must be changed. It is a very abundant species, and varies a good deal. The Canadian specimens were collected by T. C. Weston. H. MICANS.--This is a long slender cylindrical species, with a nearly circular section. The rate of tapering is so small, that it amounts to scarcely half a line in length of eighteen lines, where the width of the tube is from one to two lines. The largest specimen collected is two and a-half lines wide at the larger extremity, and if perfect would be four or five inches in length. The operculum does not show distinctly a division into a dor sal and ventral limb. It is of an ovate form, depth somewhat greater than the width, the nucleus about one-third the depth from the dorsal margin. Externally it is gently concave in the ventral two-thirds of the surface; a space around the nucleus is convex, and finely striated concentrically. On the inner surface. there is a small pit at the dorsal third of the depth, indicating the position of the nucleus. From this point radiate ten elongate ovate scars, arranged in the form of a star, the rays towards the ventral side being the longest. None of these scars quite reach the margin. The shell and operculum are thin and of a finely lamellar structure, smooth and shining. Occurs at Bic and St. Simon; also at Troy, N.Y. Collectors, T. C. Weston and S. W. Ford. Sometimes numerous small specimens from half a line to three lines in length are found with the operculum on the same slab. This shell appears to me at present to constitute a new genus, differing from the majority of the species of Hyolithes in its circular section, the operculum not divided into dorsal and ventral lines, and in the remarkable system of muscular impressions on the interior. Barrande has figured an operculum of the same type, differing from this in having only three instead of five pairs of impressions. They are, however, arranged on the same plan in both the Canadian and Bohemian species.* It is possible that our species may be a Salterella. H. PRINCEPS.-Shell large, sometimes attaining a length of three or four inches, tapering at the rate of about three lines to the inch. In perfectly symmetrical specimens, the transverse section is nearly a semicircle, the ventral side being almost flat, usually with a slight convexity, and the sides and the dorsum uniformly rounded. In many of the individuals, however, one side is more abruptly rounded than the other, in consequence of which the median line of the dorsum is not directly over that of the ventral side, and the specimen seems distorted. This is not the result of pressure, but is the original form of the shell. Sometimes, also, there is a rounded groove along the median line of the dorsum. The latter is somewhat more narrowly rounded than the sides. Lower lip uniformly convex, and projecting about three lines in a large specimen. Surface with fine striæ and small sub-imbricating ridges of growth. These curve forwards on the ventral side. In passing upwards on the sides, they . • Systême Silurian, &c., vol. III., pl. 9, fig 16 H, and fig. 17. at first slope backwards from the ventral edge, and then turn upwards and pass over the dorsum at a right angle to the length. When the width of the aperture is seven lines, the depth is about five. The operculum has not been identified. Collected by T. C. Weston at Bic and St. Simon. FIG. 5. Interior of the ventral valve of 0. gemma, enlarged about five diameters. aa, the two small scars at the hinge; bb, the two central scars; c, the smal! pit near the hinge; dd, the two principal muscular scars; g, the groove in the area. 6. Interior of the ventral valve of O. desquamata, Hall, enlarged 24 diameters. 7. Interior of the ventral valve of Obolus Apollinis, Eichwald, copied from Davidson's "Introduction to the study of the fossil Brachiopoda." GENERIC CHARACTERS.-Shell unarticulated, ovate or suborbicular, lenticular, smooth, concentrically or radiately striated, sometimes reticulated by both radiate and concentric striæ. Ventral valve with a solid beak and a small more or less distinctly grooved area. In the interior of the ventral valve there are two elongated sub-linear or petaloid muscular impressions, which extend from near the hinge line forward, sometimes to points in front of the mid-length of the shell. These are either straight or curved, parallel with each other or diverging towards the front. Between these, about the middle of the shell, is a pair of small impressions, and close to the hinge line a third pair, likewise small, and often indistinct. There is also, at least in some species, a small pit near the hinge line, into which the groove of the area seems to terminate. In the dorsal valve there are six impressions • Engraved from a figure kindly drawn for me by Thos. Davidson, Esq., F.R.S., of Brighton, England. The specimen is from the original locality of the species, Troy, N.Y. Collected by T C. Weston corresponding to those of the ventral valve, and sometimes an obscure rounded ridge along the median line. If we compare the interior of the ventral valve of an Obolella with that of Obolus Apollinis, we see that there are six muscular impressions in each, but not arranged in the same manner. The two small scars aa at the hinge line are most probably the same in both genera. The two lateral scars bb of Obolus have no homologue in Obolella, unless they be represented by the two large ones dd. Should this be the case, however, the great difference in their position, would no doubt be of generic value. I think it more probable that the large scars dd of Obolella reprepresent the central pair ce of Obolus. Again, Eichwald says that in the interior of the ventral valve of O. Apollonis there is a longitudinal septum (shown in the above fig. 7 at s), which separates the two adductors cc, and extends to the cardinal groove (I suppose he means the groove g on the area).* No such septum occurs in any species of Obolella. I have not seen any description of the dorsal valve of the O. Appollinis sufficiently perfect to afford a means of comparison with that of Obolella, but the differences in the ventral valve alone are so great that the two genera can scarcely be identical. They are, however, closely related, and occur in nearly the same geological horizon. In the rocks below Quebec and at the Straits of Belle Isle, we find the following species of Obolella : 1. O. desquamata, Hall, vol. 1, p. 292, pl. 80, fig. 2. = Avicula? desquamata, Pal. N.Y., 2. O. crassa, Hall Orbicula? crassa, op. cit. p. 299, pl. 79, fig. 8. Occurs at Troy. = 3. O. colata, Hall, Orbicula colata, op. cit. p. 290, pl. 79, fig. 9. Occurs at Troy. 4. 0. gemma, n. sp. 5. O. circe, n. sp. 6. O. chromatica, Billings, has been found as yet only at the Straits of Belle Isle. The following are new species: O. GEMMA.-Shell very small, about two or three lines in length, ovate, both valves moderately convex and nearly smooth. Speaking of the adductors, he says: "Une crête longitudinal occupe le milieu des dernières impressions et arrive jusqu'au sillon cardinal." (Lethea Rossica, vol. 1, p. 925.) Ventral valve ovate, the anterior margin broadly rounded, with sometimes a portion in the middle nearly straight; greatest width at about one-third the length from the front, thence tapering with gently convex or nearly straight sides to the beak, which is acutely rounded. The area is about one-fifth or one-sixth the whole length of the shell, with a comparatively deep groove, which extends to the apex of the beak. The dorsal valve is nearly circular, obscurely angular at the beak, and rather more broadly rounded at the front margin than at the sides. In the interior of the ventral valve there are two small muscular impressions of a lunate form, close to the cardinal margin, one on each side of the median line. A second pair consists of two elongate sub-linear scars, which extend from the posterior third of the length of the shell to points situated at about one-fourth the length from the front margin. These scars are nearly straight, parallel or slightly diverging forwards, and divide the shell longitudinally into three nearly equal portions. Between them, about the middle of the shell, are two other small obscurely defined impressions. There is also a small pit close to the hinge line. and in the median line of the shell. In the interior of the dorsal valve there is an obscure rounded ridge which runs from the beak along the median line almost to the front margin. Close to the hinge line there is a pair of small scars, one on each side of the ridge. The other impressions in this valve have not been made out. The surface of both valves is in general nearly smooth, but when well preserved shows some obscure concentric striæ. This species is closely allied to O. chromatica, the species on which the genus was founded, only differing from it, so far as the external characters are concerned, in being much smaller, and the beak of the ventral valve more extended. Occurs at Bic and St. Simon. Collected by T. C. Weston. O. CIRCE. Ovate, front and sides uniformly rounded, posterior extremity more narrowly rounded than the front, length and width about equal, greatest width at the mid-length, rather strongly and uniformly convex, surface nearly smooth, but with fine concentric striæ. Length seven lines, width a little less. The rostral portion of the shell is much thickened for about one-fifth the length, and in this part there is a deep and wide groove. In front of the thickened portion the muscular impressions are indistinctly |