but there are ten in a series, a number found in no other carnassier with which we are acquainted."

It is impossible to doubt that the expressions "quelque Didelphe" and "celles des Sarigues" must have been employed to intimate that the fossil animal was a pouched mammal,— in other words that it belonged to the order Marsupialia, Geoffroy, and undoubtedly closely related to the didelphs. His remark upon the number of molars also shows that he believed even then that this mammal, when farther studied, would be regarded as a distinct genus.

At any rate, however, this opinion confers great importance on this small relic of a jaw, not more than nine or ten lines in length, because it indicates the presence of terrestrial mammals in rocks of more ancient deposition than the chalk.

Cuvier having never had these fossil jaws in his own cabinet, having been unable to compare them with the skeletons of existing species which were brought together in his extensive collection of comparative anatomy, but merely having received the drawing, made by M. Constant Prevost, of the jaw in the Oxford Museum, and also that of a larger but less perfect one, preserved in the Museum of the Rev. C. Sykes, did not treat of these remains in a special memoir, in which he might have endeavoured to establish their relations with other vertebrated animals.

From this time, geologists, confiding in the authority and judgment of the great anatomist, have cited the Stonesfield "Didelphis as an exception to the generally-received law, that fossil mammals are not to be met with in the beds belonging to the secondary period; more recently, however, doubts have been raised by naturalists and anatomists, concerning this determination.

It has been made known that these remains of Vertebrata were regarded as having belonged to the class Reptilia: this opinion is said to have originated with Professor Grant, in the German translation of Dr. Buckland's Bridgewater Treatise, by M. Agassiz.

If this new determination could have been applied without contradiction to the half jaw examined by Cuvier, it would have had the advantage of restoring to the order of hithertoobserved phenomena, the nature of the animals from the Stonesfield beds; but M. de Blainville has again rendered the opinion uncertain, in the elaborate memoir lately read by him before the Academy, and published in the eighth number of the Comptes Rendus' for 1838,2 under the title of 2 For a translation of M. de Blainville's Memoir, see 'Mag. Nat. Hist.' p. 639.-Ed.

1838,

"Doubts concerning the supposed fossil Didelphis from Stonesfield, &c."

This celebrated anatomist having had at his disposal only the drawings of these interesting fossils, which are more or less faithful representations, has nevertheless, with his usual precise method of comparison, scrutinised the different parts of these jaws; he has put forward in succession all the difficulties to be overcome; and placed us in possession of the doubts which the previous opinions had left in his mind: and finishes by coming to this conclusion.

First. That it is not probable that the two solitary fossil fragments from Stonesfield can belong to a mammal of the genus Didelphis, or to a carnassier allied to the Insecti

vora.

Secondly. That if we ought to regard them as belonging to the class of mammals, their molar dentition would bring them nearer to the family of the seals than to any other.

Thirdly. That it is more probable that they should be referred to a genus of the sub-order of saurians.

Fourthly. That in the present state of the case he proposes to distinguish them under a distinct generic name,-that of Amphitherium.

We thus perceive that this distinguished professor of comparative anatomy is inclined to regard these vertebrated animals as more nearly allied to the Reptilia than to any other class; and he cites, in support of his conjectures, the opinion of M. Agassiz, whom he believes to entertain the same views of the matter as himself.

I ought here to observe that the note extracted from a letter of M. Agassiz which is placed at the head of No. 10 of the 'Comptes Rendus de l'Academy,' seems in favour of this opinion, since it says, "M. Agassiz, on the occasion of a recent communication from M. de Blainville, writes word that subsequently to the year 1835, he has expressed, in Bronn and Leonhard's Journal, (p. 186, anno 1835), an opinion perfectly agreeing with that of M. de Blainville concerning the supposed Didelphis." In referring however to this quotation I find that in this note M. Agassiz establishes, in a very clear manner, the opinion that the Stonesfield animals are undoubtedly mammals, but that their affinity with the marsupials does not appear to him to be so certain ;-that their teeth resemble more those of the Insectivora, and also have some resemblance to those of the seals.

The object of M. Agassiz therefore in this note, is to show that these bones are those of a mammal, which he considers rather as belonging to the order Insectivora than to any other.

M. de Blainville concludes his task by an invitation for fresh observations, which may furnish new elements to the argument, for or against the opinion hitherto admitted.

The memoir of M. de Blainville proves, that if he had had the advantage of examining the fragments themselves, he would have left no doubt upon the subject.

Having myself been more fortunate, I hastened in some sort, to reply to the appeal which he made, in the name of the Academy, and it is this which has determined me to request to-day, permission to read the memoir which I now submit to your approval.

Dr. Buckland has just brought over, among other very valuable geological specimens, the two jaws found in the schist at Stonesfield, and preserved in the Oxford Museum. He very willingly entrusted them to me during his stay at Paris, and allowed me to have models of them taken, which I have presented to the Academy. I have compared the originals with the different mammals and reptiles in the cabinet of the Jardin des Plantes, and I believe that I have arrived, by this comparison, at a confirmation of the justice of Cuvier's opinion.

One of the two jaws submitted to my examination is the very one which Cuvier for a short time inspected; the Didelphis Prevostii. The other, subsequently discovered, is of the same species as that described and figured by Mr. Broderip, his Didelphis Bucklandii.

Another jaw, which I believe to be of this latter species, makes a part of Mr. Sykes's collection. It is this specimen which Messrs. Phillips and Lyell allude to when speaking of the fossils in their works.

This specimen, which I am able to refer to, from the drawing sent by Mr. Phillips to M. Cuvier, and which M. Laurillard has had the goodness to lend me, is less complete than the two others, for the angle is wanting, as well as the condyle, and the largest part of the ascending ramus; the latter however has left its impression upon the stone, which serves as a matrix.

This proves that we now have four of these jaws belonging to two distinct species of vertebrated animals; and so far I perfectly agree with M. Agassiz, who appears to have seen a fifth, and who remarks, it is singular that we have never yet discovered any bone belonging to any other part of the skeleton.

The jaw first known has been so fully described by M. C. Prevost, in his memoir upon the Stonesfield fossils, that it will be needless to recapitulate here any details of its general form.

I have observed however, in the bone itself, that the molar teeth, which are, as you are aware, ten in number, are all pressed closely one against another; that the five or six anterior teeth have two visible roots; a triangular and pointed crown, with a little "talon" on each side, the anterior being more acute, the posterior more obtuse; that these latter, when their outer side is shown, present a crown terminating in two nearly equal conical points, with a little "talon" behind.

The second piece of jaw is a horizontal left ramus, with its inner side visible. This fragment, which is curved like the jaw of the Did. murina has a high coronoid process, enlarged, rounded, and bent a little backward. The condyle, which is very distinctly seen, is placed a little above the dental line. The angle of the jaw is prolonged into a " languette mience," making an obtuse angle with the inferior line and the horizontal ramus. One thing very important to point out, because it is a fact not previously verified, is, that this ramus shows the opening of the dental canal, which is a small circular foramen, pierced a little forwarder than that of the D. murina. The symphysis is entire and distinctly apparent. It has a rough, oval, oblong surface, which equals in width a quarter of the jaw, and which is obliquely truncated inferiorly, as we observe in the Mammalia.

The teeth remaining upon the dental arch, are three anterior grinders, exactly in their right place; they are shaped like those left in the other fossil jaw; that is to say, they are compressed, triangular, and with two small "talons" on each side. At the base of the ascending ramus we observe a posterior, imperfect molar tooth, out of its place, and displaying two very distinct pointed tubercles. There is upon the matrix and in front of the three teeth, an impression which appears to have been caused by a fallen tooth. By measuring with a pair of compasses the void space comprised between the base of the ascending ramus, and the teeth which are still in their places, and also that occupied by the same three teeth, it is easy to convince ourselves that the interval ought to be occupied by five teeth; which brings the total number of the grinders to ten, as in the other jaw.

The anatomists who are my auditors, will be able to perceive from what I have just observed of the presence of the condyle, of the form of the teeth, of the aspect of the ascending ramus and of the symphysis, the opening of the dental canal, and the prolongation of the angle of the jaw into an apophysis which is slender and compressed into the form of a tongue, that the animal which exhibits these characters is a Mammal. But that which will complete the description

and remove all doubts, is, that this jaw, like that of the Didelphis Prerostii, is formed of a single bone; while in the saurians, it is well known that each half is formed of five osseous pieces.

The inductions which have been drawn from the lobulated character of the teeth in these animals, appear to me to prove that this configuration has been greatly exaggerated. Let us only examine the false molars of a carnivorous animal, a panther for instance-and we perceive that they are also formed of a middle tubercle, compressed and triangular, having on each side a little "talon" or tubercle. There is nothing more in the teeth of the Stonesfield fossil. This sort of palmated appearance is not at all similar to the flattened and triangular teeth of some of the saurians, which have, as in the Iguanas, their edges notched in very fine regular indentations.

This comparison leads me back to the osseous fragment possessed by Mr. Sykes. This jaw, belonging to the right side, has its external surface visible; its ascending ramus and symphysary portion are wanting. We perceive in it nine distinct teeth, and the socket for a tenth. The artist, who was not an anatomist, has represented the teeth as with crowns divided into lobes, to the number of five, and forming a sort of "rosace", which never exists either in the Mammalia or Reptilia. It appears to me that these organs have not been properly detached from their matrix, and that persons have been led into error as to the palmated division of these teeth.

Having thus given the reasons which prove to me that the animal to which the fossil jaws discussed in this memoir have belonged, must have been a mammal, let us examine to what order it ought to be referred.

I apprehend that what has led us from the truth has been the comparison made between these fossil animals and the common opossum (Didelphis Virginiana). We see, in fact, in this animal, that the second false molar is much higher than those next to it, and that it differs from them. But let us take, as a point of comparison, the D. murina, which is a small didelph of about the same size; and we shall find the resemblance more striking, and shall no longer wonder at the affinity indicated by M. Cuvier. In this animal the false molars are of the same height, and are equally pressed one against another; they are, like nearly all the false molars of the true carnassiers, triangular, and have on each side a small supplementary tubercle. The posterior molars, like those of the fossil which I have in view, have two points, succeeded by a small "talon," upon the outer edge, and three conical and