II. Notice on the Fossil Beaks of four extinct Species of Fishes, referrible to the Genus Chimæra, that occur in the Oolitic and Cretaceous Formations of England. By the Rev. Wм. BUCKLAND, D.D. F.G.S., Professor of Geology and Mineralogy in the University of Oxford.*

ABOUT six years ago, Sir Philip Grey Egerton procured from the Kimmeridge clay of Shotover Hill, near Oxford, five remarkable fossil bodies of most curious configuration, in some degree resembling beaks of Cuttlefishes and Turtles, but not reducible to any known form in either of these families.

In 1832, the Rev. C. Townsend of Great Milton, near Oxford, discovered in the Portland stone of that village another series of bones, resembling those from the Kimmeridge clay, but very much larger, and of a different species.

On my submitting these specimens to Mr. Mantell, he immediately compared them with three similar bones in his collection, one from the Chalk marl of Hamsey, and two from the Chalk near Lewes. These were obviously the same parts of two other species of animals of the same genus. That from the Chalk marl had been shown by him to Cuvier, who could only recognise in it a distant resemblance to the articulating posterior portion of a jaw of a Saurian; but this resemblance was not maintained in the more perfect fragments of other species which had come into my possession from the Kimmeridge and Portland beds.

Mr. Mantell permitted me at this time to prepare a drawing of the fragment from the Chalk marl which he had submitted to Cuvier.

After searching in vain through the best collections in London, and consulting our best comparative anatomists, I could find no animal whose beak or jaws corresponded with either of the forms of fossil bones under consideration.

During the last five years I have lost no opportunity of submitting these fossils to skilful comparative anatomists, and with the same result. My exhibition of several of them to some of the most distinguished anatomists of Germany, at the meeting of the Naturforscher at Bonn in September last, threw no further light upon the subject. The nearest approximation that was suggested to me came from Professor Carus, who advised me to compare the two smallest of these fossils (evidently a pair) with the beak of a Tetrodon.

In pursuance of this advice, I examined all the Tetrodons in every museum I visited after my departure from Bonn, and arrived at no other conclusion than the assurance that * Communicated by the Author. This paper was read before the Geological Society on the 4th of November, 1835.

not one of these supposed fossil beaks could be referred to that genus.

In examining the rich collection in the museum at Leyden, a few days ago, with my friend Professor Van Breda, I found by the side of a Tetrodon a skeleton of that rare fish the Chimæra monstrosa, of which I had never before seen the bones, and instantly recognised in the upper and lower jaws of this animal the object of my long research. The two intermaxillary bones of the upper jaw corresponded with the pair of toothlike bones from the Kimmeridge clay, which I had in vain compared with the teeth of the Tetrodon; the superior maxillary bones corresponded with a second pair of the fossil bones from the same clay; and the lower maxillary of the Chimera presented the form of the fossil inferior maxillary bones of my four different species from the Portland stone, Kimmeridge clay, Chalk marl, and Chalk.

This discovery of the type of each of these new forms of fossil bones in the mouth of a living species of Chimæra, at once clears up all the difficulties of which I have so long been seeking the solution, and enables me to announce the existence of four fossil species of a genus hitherto unheard of in the annals of Paleontology; one in each of the following four different formations, namely, the Portland stone, Kimmeridge clay, Chalk marl, and Chalk. To that discovered in the Portland stone, I propose to give the name of Chimæra Townsendii; to that in the Kimmeridge clay, Chimera Egertonii; to that in the chalk marl, Chimæra Agassizii; and to that in the chalk, Chimara Mantellii.

On my submitting these fossils to Professor Agassiz, he at once admitted them to belong to the genus Chimæra, a genus of which the living individuals are extremely rare, and of which he knows not where a single prepared skeleton exists, except in the museum at Leyden.

The only known living species of the genus Chimæra is widely diffused, and is usually found pursuing herrings and migratory fishes: it lives chiefly in the northern seas, and occurs also in the Mediterranean. It is most nearly allied to the family of Sharks, and is from two to three feet long. The cartilaginous nature of its skeleton explains the reason why no other bones of the fossil Chimæra have been found, together with those that form their very peculiar jaws. The hard horny plates which cover these jawbones in the living species, and perform the office of teeth, are in none of our fossil specimens preserved. The two intermaxillary bones of the upper jaw of the Chimera Egertonii have nearly the hardness of enamel, and appear to have had no separable horny covering: the

superior and inferior maxillary bones of the same species exhibit rugous surfaces of attachment, from which their horny coverings have been removed. The same marks of attachment are seen in the lower jaw-bones of the Chimara Agassizii and Chimera Mantellii. The horny investment of all these bones has evidently fallen off and perished, like the horny covering which separates readily from the bony beak of Turtles, and which is rarely, if ever, found with the bones of fossil Testudinata.

The genus Chimera is one of the most remarkable among living fishes, as a link in the family of Chondroptérygiens. The fact of the existence of many fossil species of this curious genus (and some of these much larger than the single known existing species) in such early periods as those of the Oolitic and Cretaceous formations leads to important considerations in Physiology.

Professor Agassiz has at my request prepared the following description of the four fossil species which form the subject of this communication. Further details and figures will be published by him in the eighth number of his Poissons Fossilęs.

Note by Professor Agassiz.

The discovery of the genus Chimæra among fossil fishes is one of the most interesting and unexpected.

Recent Chimæras are very little known, and have been arranged in the order of cartilaginous fishes, but their organization, and especially the structure of their skeleton, has not been sufficiently studied. Dr. Buckland's discovery will draw the attention of Ichthyologists in a particular manner to this singular family. The four fossil species about to be enumerated differ essentially from each other, and are considerably larger than the living. Unfortunately the fossil fragments which we now possess are far from being complete; only the jaws of these curious fishes have hitherto been discovered, and principally the lower jaws.

In the Portland species, the Chimæra Townsendii, which is the largest, the inferior maxillary is very large, short, and proportionally much thicker, the groove of the symphysis of its two branches shallower, and the cavity of the dental edge broader than in the other species; its exterior surface is convex and furrowed longitudinally with shallow wrinkles. The intermaxillary bone is much bent.

In the Chimæra Egertonii the inferior maxillary is short and flat; its snout is truncated, and in proportion very large; the cavity of the dental edge is very wide and the groove of its symphysis very deep; the intermaxillary is much bent, and

the dental edge truncated and square; the superior maxillary is irregularly triangular, much elongated, and contracts insensibly towards its dental extremity, which is bifid.

In the Chimara Agassizii of Dr. Buckland the inferior maxillary is the most regular in form of the four species; it is nearly square, and has the dental edge slightly open; the surface of the symphysis is flatter than in the other species.

:

The Chimera Mantellii has the inferior jaw straighter and thinner its exterior surface is perfectly smooth and flat; its snout is much elongated and pointed, and the cavity of the dental edge wider.

Since Dr. Buckland's discovery of the above four species, I have found a fifth in the collection of Mr. Greenough, which differs considerably from them all, in the extreme shortness of the lower jaw, the length of which is less than its height. The symphysis of the lower jaw is flat; the dental margin truncated and grooved in its hinder part. The external surface is smooth; the middle of the inner surface concave; the intermaxillary is flatter than in the Chimera Egertonii, and terminates in a straight point. The superior maxillary is shorter than that of the Chimæra Egertonii.

I propose to give to this species of so remarkable a genus the name of Chimara Greenovii. The locality of this fossil is unknown.

Oxford, Oct. 27, 1835.

III. On the Relation between the Velocity and Length of a Wave, in the Undulatory Theory of Light. By JOHN TOVEY, Esq.

To the Editors of the Philosophical Magazine and Journal. GENTLEMEN,

IN

N the last volume but one of your Magazine, the Rev. Professor Powell presented us with an abstract of the essential principles of M. Cauchy's View of the Undulatory Theory of Light; by which, as Mr. Powell says, it appears that a relation between the velocity and length of a wave is established on M. Cauchy's principles, provided the molecules are so disposed that the intervals between them always bear a sensible ratio to the length of an undulation." vol. vi. p. 266.

Since I first read this, I have arrived at the same result as M. Cauchy by a less complicated method, which I proceed to lay before you. I do this with diffidence, having read scarcely anything on the subject besides the abstract above mentioned and Professor Airy's tract. Should you deem

my method worthy of a place in your Journal, I shall probably send you a continuation of the subject.

2

Let m, m', m", &c. be the masses of the particles of æther; let the rectangular coordinates of m be x, y, z; those of m', x+▲x,y+▲y, z+ Az; of m", x+Ax', y+^y', z+Az', &c. Let r = √(x2 + Ay2+z3), r2 = √(Ax22 + Ay12 + A≈2), &c. Suppose the masses to be all equal, and the force of one particle on another to be a function of their distance multiplied by m; and suppose each particle to be influenced only by the attractions or repulsions of the other particles; then as the cosines of the angles which r makes with the positive direcΔι Ay Az tions of x, y, z are we have (by the principles of statics), when the system is in equilibrium,

r

r

The sums & extending to all the particles within the sphere of the attractive or repulsive influence of the particle m, which may be any particle of the system.

Now, suppose the system to be disturbed, and that at the end of the time t, the displacements of m, in the directions of x, y, z, be E, n, 8; and those of m', &+A§, n+An,+AS; and suppose A, An, A to be so small that we may neglect their squares and rectangles; then the distance of these particles being r+Ar = √ [(Ax+A§)2+(Ay+An)2+(Az+AY)2], we have

The cosines of the directions which r+ Ar makes with those

of x, y, z will be A+A & Ay + An Az+A. and if we

r+ Ar r+Ar r+Ar

write X, Y, Z for the sums of the components of the forces acting on m, in the directions of x, y, z, we have