been already given by Cuvier to a genus of Annelides, could not be retained; and on the discovery of new species among some fossils from Cornwall the name Endosiphonite was proposed, as indicating the chief peculiarity in the genus, and also having analogy with the names of other fossil genera of multilocular shells.* The number of species already determined amounts to sixteen or seventeen, thirteen of them German. They are all probably referrible to the same geological period, which is one of the very earliest in which fossil remains are found.

The Spirula is a shell well known to conchologists by a recent species, and apparently very common in many parts of the ocean, but unfortunately the history of the animal whose habitation it is we are not yet able to give; for, although the shell abounds in many places, the animal is never attached, and there is even some degree of doubt as to whether it includes the shell or is included by it. In all probability the former is the case.

In the transition limestone of Œland, an island on the south-eastern coast of Sweden, there is found a fossil which has been called Lituite, but which seems, as far as can be told, to belong to this genus Spirula. Both are spiral shells, with the whorls of the spine not close to each other, as in Nautilus; and both have simple septa, and a siphuncle nearer the inner than the outer margin. As these Lituites seem confined to the transition limestone, and the Spirula has never been met with in a fossil state, it will be a very singular anomaly in natural history if these eventually prove to be referrible to the same genus; for there is no known instance of a genus being recreated after it has been once extinct.

If we conceive the shell of a Spirula straightened out, so as to present the appearance of a series of cup-like chambers placed over one another nearly vertically, we shall have the Orthoceratite, a genus so named from its resemblance to a straight horn. It is entirely confined to a few very ancient formations, although the number of ascertained species is more than fifty, and the abundance of individuals perfectly incredible. The size, too, which some species reached was extremely large; for they have been found more than three feet in length, and with a diameter of more than six inches at the opening.

• The description of this genus from the English species will be found in the forthcoming volume of the Cambridge Philosophical Transactions, where also the analogies with allied genera are more fully discussed. Count Münster's paper is translated in the Annales des Sciences Naturelles, 1834.

As many as seventy chambers have been counted in these enormous specimens.

We have thus, in the family of Nautilacea, a series of genera of chambered shells, with siphuncles running through them, the form of the shell varying from that of a straight cone to a spiral, in which all the inner whorls are hidden by the last one; and the question now to be considered is the probable amount of change in the animal economy which corresponded to these alterations of shape.

Now we know, in the first place, that the Nautilus is an entirely external shell, capable of some range in the depth at which its inhabitant lives, and therefore sufficiently strong in the structure of airchambers to resist the increased pressure arising from increased depth in the water. What conclusions shall we, then, arrive at from the structure of the Endosiphonite, where the septa are stronger, inasmuch as they present more points in their intersection with the shell, and where the pressure acts immediately upon the whole surface, and not intermediately, as in the Nautilus, where the whorls successively defend each other? It seems probable that this new genus was an external shell, sometimes rising to the surface, like Nautilus; but from the narrower and less rounded appearance of the shell, and from the shape of the septa, we should conclude that it belonged to an animal of rather greater activity, and one, perhaps, more capable of following its prey along the muddy bottom of a sea, than the inhabitant of such a shell as the Nautilus.

There seems a very great probability that the animal of Spirula incloses within its mantle the whole or greater portion of the shell; and from the close analogy of the Lituite, doubtless, that also was internal. We should expect an animal thus independent to be endowed with greater powers of locomotion than one encumbered with a house upon its back very much larger than its body; and probably all the free Cephalopods are more swimming than creeping animals. In support of this opinion the Spirula is known to be a very thin and brittle shell, and the apertures in the septa, instead of opening a simple communication from chamber to chamber, are united by a calcareous tube passing continuously from the last or outer septum into the first chamber. The size of the last chamber is also, in every known specimen, very small; and although, from the brittleness of the shell, the aperture might and would easily become injured, still, out of the number that have been seen and brought away, something would surely have been found to indicate this extension, if it had ever

existed. What the exact mode of increase in a shell like this may have been, and whether any principal organ of the body was immediately connected with the chambers, the present state of our knowledge with regard to this animal does not allow to be determined. It is to be hoped that some one of our numerous scientific navigators may follow the example of Mr. Bennett,* and, by preserving and putting into the hands of a naturalist the animal of a Spirula, set them and many other questions at rest for ever.

It is a matter of extreme difficulty to determine whether the Orthoceratite was an external or internal shell. Dr. Buckland has considered the latter as the most probable opinion; but, from the very large size of the last chamber, and the difficulty of conceiving so enormous a cephalopodous animal as to require an internal shell three feet long, we may be allowed to doubt the correctness of such an assumption. The siphuncle, too, varies so much, and was evidently so very important an organ in this genus, that we hardly know how to bring our analogies to bear in the consideration of it. If this singu lar shell was really the mere skeleton of an animal whose predaceous habits were at all proportioned to its size, we must pause with wonder and astonishment at the state of animal life in those seas which could support myriads of these giant molluscs upon the exuberance of its

stores.

There is one more question which presents itself with regard to this part of the subject, although it applies equally to other parts; and that is, whether the temperature required for the developement of these large animals in such amazing numbers was greater than is at present known in the climates where they are found. Many, indeed most, of the beds remarkably abundant in these fossils, are in high northern latitudes; and it has been imagined that a low temperature is not favourable to such extreme vitality. It may be so, but we are not justified in concluding at once that it must be so. Probably in no part of the tropical seas is there so much living matter as in an equal area in the Polar seas; and it is a well-known fact that the Whale has but to swim for a short space with its mouth open in order to satisfy its appetite, which in so huge a creature must necessarily require a large quantity of food. Still, as many other known facts concerning these early seas seem to point more or less to the

It is to the fortunate capture of an individual of the Nautilus Pompilius by this gentleman that we are indebted for the valuable memoir of Mr. Owen, which has thrown so much light on the subject of the cephalopodous animals of multilocular shells.

same conclusion, there is certainly a high degree of probability that the neighbourhood of the North Pole did not then produce that extremity of cold which now characterizes it. At all events, the general opinion at the present day is in favour of such a supposition; and we do not feel either inclined or prepared to controvert it, All we wish is, to give the reader to understand that it is a supposition, and not a matter absolutely decided.

We have hitherto, while considering the family Nautilacea, been guided in some measure by analogies which connect the fossil with the recent genera. Passing on now to the Ammoneata, we are obliged to leave behind us these glimmerings of light; and since there are, so far as is known, no living congeners of this family, we are forced to bring into operation certain rules founded on experience, and depending on two broad and general principles: viz. that no part of an animal whatever exists without its use; and that while the general structure is perfectly adapted to the wants of the species of which it is significant, so also every portion has a mutual relation with all the rest, is in itself quite perfect, and exactly fitted to the purpose assigned to it.

The extent to which this entire dependence on the perfect wisdom of the Creator may be safely carried, must be almost marvellous to any person not in the habit of studying Natural History, with enlarged and general views. But no one can call to mind its value in the hands of Cuvier, when applied to the comparative anatomy of animals of higher organization, without acknowledging that it became with him an instrument for the discovery of truth, whose astonishing power was only equalled by the sagacity of him who employed it. It remains still to be seen how far the same means of discovery may be extended to the lower forms of animal life, and the conclusions forced upon us in consequence. We have already shewn that, in applying it to the cephalopodous animals, we are descending only the first step in the scale of organization from the vertebrata (the object of Cuvier's researches), and thus, in the case before us, we are entitled to look with considerable confidence to that dependence of structure on organization which certainly becomes less strongly marked as we approach the limits separating the animal from the vegetable exist

ence.

Proceeding on these principles, we assume the position of the siphuncles in multilocular shells as the distinctive character of two great families, because we find this character accompanied by a very remarkable change in the coutrivances which indicate strength, and

thus feel warranted in concluding that a corresponding alteration existed in the structure of the animal inhabitant. We then proceed to subdivide these larger into smaller and more convenient groups, and consider the external appearance as a sufficient generic character, because on that chiefly seems to depend the fact whether the body of the animal was included within the shell or included it. Bearing in mind this distinction, there may be mentioned five well-defined and easily-known genera of Ammoneata, which are called Turrilites, Scaphites, Ammonites, Hamites, and Baculites, all having a dorsal siphuncle, and its walls of separation between the chambers being in all more complicated, and stronger than is generally the case in any genus of Nautilacea. As in that family we first explained the mere technical facts relating to each genus, and then enlarged a little on the probable nature of the animal, so we propose now, following the same course, to inform the reader, first, of what is known with regard to these extinct genera; and then to indulge in some of those curious speculations which the subject is so well calculated to introduce.

The order in which we have arranged the known' groups abovementioned is not of much consequence, perhaps; but, as it departs from that usually employed, we may as well observe that the names are not thrown together thoughtlessly, but arranged on a principle which, for our purpose, is convenient enough. First, taking the most complicated form, we have named the Turrilite, which is a spirally twisted shell, not developed on one plane. In fact, its shape resembles that of a Snail, and many other common turreted shells, too well known to require mention. The next, Scaphite, is named from a Greek word signifying a boat, and may be compared to an Ammonite whose last whorl is separated from the rest, and after being extended for a short space in a straight line, is again bent round to meet the rest of the shell. The Ammonite is a simple spiral, with the whorls contiguous and developed on one plane; the Hamite more resembles a hook (whence its name), the whorls not being contiguous, and the Baculite (so called from its similarity to a staff), is quite straight, and usually in the shape of a long right cone with an elliptic base.

The Turrilites, and indeed all the other Ammoneata, except the Ammonites, are confined to very narrow limits of geological distribution, being rarely found in any formation anterior to the lower greensand, though they do occasionally appear in the oolites. There is one species of Turrilite described as occurring in the coral rag of the