A fourth species, consisting of a portion of the superior jaw, has been found in the calcaire grossier, in the department of Orne.

M. Cuvier has been able to satisfy himself that all these species are distinct from each other, as well as from the living species.

The specimen before us bears the nearest comparison with the first of the above named species, but is sufficiently distinguished by the larger size, relative proportions, and number of teeth of the Appenine species.

Description of D. Calvertensis.—In general outline, resembling other skulls of this genus. The head is proportionably narrower, and snout more elongated, than the Italian specimen with which I have compared it. The occipital and temporal ridges are strongly developed, indicating muscular strength, especially of the jaws, We find similar indications in the remains of the teeth, which have been large and robust. There are ten sockets remaining on the right side, with the teeth broken off at the rim. These organs approximate each other. The ten sockets include a line four and a half inches long. There has been about one and a half inches of the end of the snout broken off, which would afford room for two or three more teeth-making twelve or thirteen, in all, on each side. The pyramidal eminence, anterior to the posterior nares, on the palatine surface, is strongly pronounced. It terminates opposite the last tooth. The excavations or longitudinal grooves, on each side of the upper portion of this eminence, are unusually deep. The palatine surface is slightly convex transversely. Above, the head is narrower across the occipital ridges than other allied species, and narrower than the transverse diameter of the base of the skull. The ossa nasi are longer than broad, and convex. The atlas vertebra adheres to the occiput, above the condyles. It measures, across the transverse processes, five inches; transverse diameter, three inches; and the ring is about one inch thick.

In the following admeasurements, one and a half inches must be considered as the length of the last portion of the extremity of the snout.

Dimensions.—Total length of head, from the temporal crest to the presumed extremity of the jaw,

From the anterior borders of the spiracles to the presumed ex

tremity of snout,

Breadth of skull above, across the occipital crests,

Breadth at base, between the temporal bones,

Longest diameter of largest tooth at the socket,

17 inches.

measure.

3 tenths.

The head of the Appenine species is one foot, ten inches, nine lines long, French The spiracles are one foot nine inches, from the extremity of the snout, The accurate figures which accompany this description, will render further de. tails unnecessary.

Geological Series: Middle tertiary of Maryland.

Description of the Plates.

Figure 1.-Basal view of the skull.

Figure 2.-Superior view of the skull.

Figure 3-Lateral view of the skull.
Figure 4.-Occipital view of the skull,

Sketch of the great Geological Features of the Valley of Connecticut River, at Charlestown, New-Hampshire, and Remarks on some Crystals found in the Slate-rock scattered in that region; with specimens.

The valley of the Connecticut river, in its widest extent, may be said to be in. cluded between the summits of the Green Mountains of Vermont on the west, and those of the granite ridge, forming the height of land between it and the valley of the Merrimac, on the east. From the edges of the proper valley in which its waters flow, there is a continual though broken rise to these great boundaries, from whose sides flow the tributary streams of the river. The immediate valley is bounded by a steep ridge of hills on either side, between the feet of which and the river spreads an extent of fertile meadow; the deposit of the river, through which it winds its way, alternately approaching to and receding from these ranges of hills. The nucleus and substance of these hills in Charlestown, consists of strata of argillaceous slate, upturned nearly perpendicularly, the direction of the strata being nearly north and south, and the dip a little to the south of east. On the east side, passing over the summit of this first ridge, there is a slight valley, beyond which rises a ridge of granitic structure, seeming as if forced up through the chasm made by the depression of the eastern edge of the slate strata forming the first ridge, and holding them in place by its pressure on the inverted edge and sloping surface. Somewhat the same arrangement is to be found on the western side. The following is a sketch:

A. Strata of slate.
B.S

C C. Granite ridges.

d d. Earth and coarse gravel forming the outer surface of the hills, in many places stratified, and resembling the deposits in the bed of a river.

e e. Meadows or interval land, consisting of fine silt.

G. River.

g. Plain of fine yellow sand, with a slight covering of vegetable mould, upon which stands

f. The village of Charlestown.

The arrangement is not, however, altogether so simple as is represented in this sketch. The granite is often intermixed with beds of gneiss, many of them upturned like the strata of slate, and running parallel to them. These, as well as the slate, are seamed with veins of quartz, and sometimes of calcareous spar; and there are all gradations of slaty structure, from gneiss to argillaceous slate. In some places the slate is wanting, and the granite approaches close to the river, and even extends into it. On the Vermont side, beds of limestone occur occasionally be. tween the slate and the granitic rocks.

The soil of the hills, in the eastern part of Charlestown, abounds in fragments of slate, of a coarse texture, with numerous specks of black mica, and sometimes with small garnets, seemingly one of the varieties between argillaceous and mica slate. These fragments are of all sizes—from a mere pebble to the weight of many tons; some much worn, and others rough and angular, and with considerable dif. ference in fineness of texture. They are all characterized, however, by the presence of numerous crystals, of a curious character, which form the more immediate objects of this paper, and of which I have the pleasure to send the National Insti. tution a number of specimens; an end of each of which I have cut and slightly polished, for the purpose of showing more readily the structure.

These crystals have been variously denominated by different persons who have seen them, though no one appears to have given any careful description of them. One of the first persons who mentioned them to me, when I came into this part of the country to live, spoke of them as being crystals of staurotide; another after. wards called them macle, (and they are so termed in Cleveland's Mineralogy,) while Dr. Jackson, in the last report of his geological survey of New-Hampshire, speaks of them as macle, or (apparently as synonymous) hemitropic andalusite. They are certainly of considerable variety of structure, under a general similarity of configuration; and, while agreeing exactly with none of the minerals described under the foregoing names, have yet points of resemblance with each.

Staurotide, or granatite, as called by some, belongs to the garnet family, and macle and andalusite are of the feld-spar family, if macle be, as I presume, the same as chiastolite, according to the nomenclature of Jameson. His description of the mineral, to which he gives this name, is, as far as my recollection serves, almost precisely the same as that which Cleveland gives of macle.

The staurotide consists of two six-sided prisms, intersecting each other either at right angles or obliquely. The crystals in question are sometimes found in this form; and two of the specimens I send herewith, afford instances of it-one being an intersection nearly at right angles, and the other an oblique intersection, at about forty-five degrees. The generality of the crystals are, however, single, consisting of four-sided prisms, the bases of which are either rhomboids or rhombs. In the most perfect crystals, the latter shape is the prevalent one, and the figure is often very exact, the angles being extremely well defined. They have also a natural cleavage through the shorter diagonal of the rhomb, by which they are divided inte two triangular prisms. Now Haüy shows that the primitive form of granatite is a quadrangular prism, the bases of which are rhombs, with a similar cleavage through the shorter diagonal of the base, The angles of the rhombs he makes to be about 130° and 50°, which agrees with the measurement of some of the most perfect of these crystals.

Some of them also agree with staurotide in other external characters, as the dark, reddish, brown color, the internal glimmering lustre between vitreous and re. sinous, in the general character of the fracture, in opacity, with occasional trans. lucency, in hardness, brittleness, and infusibility. Yet still the specimens, in which these last characters are best marked, are precisely those which I have always found single, with rhombic or rhomboidal bases, and not intersecting each other. Those so intersecting have a different set of characters, apparently belonging more to the description of macle or chiastolite, yet not precisely agreeing with that,

Macle or chiastolite is described as being always crystallized in nearly rectangular four-sided prisms. When, however, the end of the prism is carefully examined, there will be perceived in it a blackish prism enclosed in the larger one, which is of a greyish, yellowish, or reddish white color. From each angle of the central prism a blackish line passes to the corresponding angle of the outer prism; and in each of these external angles there is commonly a small prismatic space, filled with the same black matter as that of which the central prism is composed, which is a dark clay slate, the same as the rock in which the crystal is imbedded.

As was before observed, Cleveland's description agrees with this, though, in conjunction with a figure corresponding to this description, he gives, as another variety, I think, a figure of a crystal with a rhombic base, the marking of which agrees very well with some of my specimens. I have never found any of these crystals rectangular, and but few approaching to that shape.

In the most perfect specimens, the whole rhomboidal crystal seems to be enveloped in a uniform coat of black, slaty matter, of a very fine grain, and easily admitting of considerable polish. When a cross section is made, (and it usually breaks in these specimens pretty smoothly,) and the surface ground down and polished, it will be seen that this thin black casing encloses a substance of a reddish yellow color, of glistening and somewhat foliaceous or sparry appearance, sometimes opaque, sometimes slightly translucent. This yellowish substance encloses a smaller hollow prism, of the same blackish matter, marked merely by a thin black line, and within it is contained the same reddish yellow matter, as filled the space between it and the outer coating; giving, in fact, the appearance of a small prismatic crystal, of yellowish matter, with a blackish coat inserted in the centre of a larger crystal, of the same color, while small black lines pass from the angles of the inner case of black matter, to the corresponding angles of the outer. These black lines are very feint and delicate in the transverse diagonal of the crystal; thicker and more strongly marked in the longitudinal diameter; spreading a little as they approach the outer casing, so as to give the idea of being formed by a duplicature of that investment. In one or two crystals, indeed, this formation is distinctly marked.

In other crystals, less perfect, the bases are more generally rhomboids than rhombs. The outer black case is thicker, the yellowish contained matter less regular in its figure, (the angles being rounded off,) and, instead of an inner crystal resembling the outer, it is divided, by transverse diagonals of the black matter, into four portions. In some specimens these are very small, appearing on the section merely like dots, while the bulk of the crystal is composed of the blackish coat, which in these is rather grey than black. In other instances there is no regular figure to the contained matter, but it is dispersed through a black crystal, in irregu lar patches, giving to the section a mottled appearance.

Although the disposition of the separate parts differs from the description, I have looked upon these two varieties as macle, but of a different variety from that commonly described. Yet it is among the second variety that I have found very good specimens of the intersection of crystals forming a cross.

In a third variety, there is no yellowish contained matter to be distinguished. The crystals consist wholly of blackish or grayish matter, sometimes with and

sometimes without a central spot corresponding with the shape of the crystal, of a different tint or texture from the reet. One or two of these that I send, have a reddish tinge in the gray, and I have conjectured that some more strongly tinged varieties of this kind may have induced Dr. Jackson to speak of them as anda. lusite; to which, otherwise, I have seen no resemblance in any crystals I have examined. Andalusite is usually hard enough to make a slight scratch upon quartz ; while these grayish crystals may be cut or scraped with the point of a knife. This variety also affords instances of intersection.

As a fourth variety, I have ranked those described as resembling granatite in external characters, other than the hexagonal shape and crossing. In some of these, while the texture of the crystal seems the same, the insertion of the internal crystal, and the connecting lines of the angles, are distinctly marked by a light furrowed line, as of a joining. Some variety of this kind may be that of which Dr. Jackson speaks. He obtained his specimens from a locality several miles dis. tant from me, and which I have never examined.

SPECIMENS.

In Package No. 1.-These are specimens of the most perfect form, having the inner crystal distinctly marked, with the diagonal joinings, and the appearance of duplicature of the outer investment to form the longitudinal diagonal. One of the specimens is triangular, being half of a crystal divided in its natural cleavage through the transverse diameter. Another is divided obliquely lengthwise, and two black lines may be observed traversing the crystal diagonally lengthwise.

Package No. 2.—This contains specimens of those described as the second variety, from the perfect form of those in No. 1, to a more central spot of the yel lowish matter, and two handsome specimens of the mottled kind. One of these specimens, with a central dot, is an imperfect six-sided prism, and is half of one of the crystals of a stauroidean formation. The remainder of the cross accompanies this package.

Package No. 3.-Specimens of the gray and blackish variety, without any enclosed yellowish matter, but one or two of them with a darker nucleus, similar in shape to the external crystal. One of the gray crystals is an instance of an oblique intersection. This specimen is split longitudinally, and shows one crystal passing through the other.

Package No. 4.-Specimens of the dark reddish, brown variety, very hard, brittle, and difficult to be detached from the matrix. One of them has a perfect formation; in the others it is not to be discovered.

Quere. Are not these last crystals radically distinct from the others, and even from the perfectly shaped one with them?

All of the crystals that I have seen, have been found in the detached masses spoken of. I have never met with them in any ledge, though others have told me that they have found them so. I have fancied, from my own observation, that they mistook the projection of some huge half-buried fragment for the outcropping of strata, as they were persons of little experience in such researches.