THE name of Nautilus Sypho* has been applied to a very curious and beautiful chambered shell found in the Tertiary strata at Dax, near Bourdeaux; and that of Nautilus Zic Zac to a cognate shell from the London Clay. (See Pl. 43, Figs. 1, 2, 3, 4.)

These fossil shells present certain deviations from the ordinary characters of the genus Nautilus, whereby they in some degree partake of the structure of an Ammonite.

These deviations involve a series of compensations and peculiar contrivances, in order to render the shell efficient in its double office of acting as a float, and also as a defence and chamber of residence to the animal by which it was constructed.

Some details of these contrivances, relating

This shell has been variously described by the names of Ammonites Atun, Nautilus Sypho, and N. Zonarius. (See M. de Basterot Mem. Geol. de Bourdeaux.)

[358 CONTRIVANCES IN NAUTILUS SYPHO] to the Nautilus Sypho will be found in the sub-joined note.*

As the place of the siphon in this species is upon the internal margin of the transverse plates (Pl. 43, Fig. 2, b¹, b², b³,) it had less power than the more central siphuncle of the Nautilus to attach the mantle of the animal to the bottom of the outer chamber. For this defect we find a

* The transverse plates, (Pl. 43, Fig. 1, a. a¹. a².), present a peculiarity of structure in the prolongation of the collar, or siphuncular aperture entirely across the area of the air chambers, so that the whole series of transverse plates are connected in one continuous spiral chain. This union is effected by the enlargement and elongation of the collar for the passage of the siphuncle into the form of a long and broad funnel, the point of which, b. fits closely into the neck of the funnel next beneath it, c. whilst its inner margin, resting upon the arch of the subjacent whorl of the shell, transfers to this arch a portion of the external pressure upon the transverse plates, thereby adding to their strength.

As this structure renders it impossible for the flexible siphuncle to expand itself into the area of the air chambers, as in other Nautili and in Ammonites, the diameter of each funnel is made large enough to allow space within it for the distension of the siphuncle, by a sufficient quantity of fluid to cause the animal to sink.

At each articulation of the funnels, the diameter of the siphuncle is contracted, as the siphuncles of Ammonites and Nautili are contracted at their passage through the collars of their transverse plates.

Another point in the organization of the siphuncle is illustrated by this shell, namely, the existence of a soft calcareous sheath, (Pl. 43, Fig. 1, b. c. d.), analogous to that of the N. Pompilius, (Pl. 31, Fig. 1, a. b. c. d.), between each shelly funnel and the membranous pipe or siphuncle enclosed within it. At Pl. 43, Fig. 1, b, wc have a section of this sheath folding round the

[369 AND NAUTILUS ZIC ZAC.] compensation, resembling that which Von Buch considers to have been afforded by the lobes of Ammonites to the inhabitants of those shells. This compensation will be illustrated by a comparison of the lobes in N. Sypho (Pl. 43, Fig. 2.), with a similar provision in the Nautilus Zic Zac (Pl. 43, Figs. 3. 4.)*

smaller extremity of the funnel a'. From c, to d, it lines the inside of the subjacent funnel a²; and from d, continues downwards to the termination of the funnel a², on the inside of e. At e, and f, we see the upper termination of two perfect sheaths, similar to that of which a section is represented at b. c. d. This sheath, from its insertion between the point of the upper siphon and mouth of the lower one, (Fig. 1, c.), must have acted as a collar, intercepting all communication between the interior of the shelly siphuncular tube and the air chambers. The area of this shelly tube is sufficient, not only to have contained the distended siphuncle, but also to allow it to be surrounded with a volume of air, the elasticity of which would act in forcing back the pericardial fluid from the siphuncle, in the same manner as we have supposed the air to act within the chambers of the N. Pompilius.

* On each side of the transverse plate in both these species there is an undulation, or sinus, producing lobes (Pl. 43, Fig. 2. a¹, a², a³, Fig. 3. a. and Fig. 4. a. b.) There is also a deep backward curvature of the two ventral lobes, Fig. 4. c. c. All these lobes may have acted conjointly with the siphuncle, to give firm attachment to the mantle of the animal at the bottom of the outer chamber. The shell Fig. l. is broken in such a manner, that no portion of any lateral lobe is visible on the side here represented At Fig. 2. a¹, we see the projection of the lateral lobes, on each side of the convex internal surface of a transverse plate; at a² we see the interior of the same lobes, on the concave side of another transverse plate; and at a³ the Points of a third pair of lobes attached to the sides of the largest air-chamber that remains in this fragment.

[360 COMPENSATIONS AND LINKS.] A still more important use of the lobes formed by the transverse plates both of N . Sypho and N. Zic Zac, may be found in the strength which they impart to the sides of the external shell (see Pl. 43, Figs. 1, 2, 3, 4.), underpropping their fiattest and weakest part, so as to resist pressure more effectually than if the transverse plates had been curved simply, as in N. Pompilius. One cause which rendered some such compensation necessary, may be found in the breadth of the intervals between each transverse plate; the weakness resulting from this distance, being compensated by the introduction of a single lobe, acting on the same principle as the more numerous and complex lobes in the genus Ammonite.

The N. Sypho and N. Zic Zac seem, therefore, to form Links between the two great genera of Nautilus and Ammonite, in which an intermediate system of mechanical contrivances is borrowed, as it were, from the mechanics of the Ammonite, and applied to the Nautilus. The adoption of lobes, analogous to the lobes of the Ammonite, compensating the disadvantages, that would otherwise have followed from the marginal position of the siphuncle in these two species, and the distances of their transverse plates.*

* In some of the most early forms of Ammonites which we find in the Transition strata, e. g. A. Henslowi, A. Striatus, and A. Sphericus. Pl. 40, Figs. 1, 2, and 3,) the lobes were few, and nearly of the same form as the single lobe of the Nautilus Sypho,

[361 SHELLS ALLIED TO NAUTILUS.] It is a curious fact, that contrivances, similar to those which existed in some of the most early forms of Ammonite, should have been again adopted in some of the most recent species of fossil Nautili, in order to afford similar compensation for weakness that would otherwise have been produced by aberrations from the normal structure of the genus Nautilus. All this seems inexplicable on any theory which would exclude the interference of controlling Intelligence.
 
 

WE have reason to infer, from the fact of the recent N. Pompilius being an external shell, that all fossil shells of the great and ancient family of Nautili, and of the still more numerous family of Ammonites, were also external shells, inclosing in their outer chamber the body

and of N. Zic zac; like them also the margin was simple and destitute of fringed edges. The A. nodosus (Pl. 40, Figs. 4 and 5.), which is peculiar to the early Secondary deposits of the Muschel-kalk, offers an example of an intermediate state, in which the fringed edge is partially introduced, on the descending or inward portions only, of the lobated edge of the transverse plates.

[362 SPIRULA.] of a Cephalopod. We further learn, from Peron's discovery of the shell of a Spirula partially enclosed within the body of a Sepia,* (see Pl. 44, Fig. 1, 2), that many of those genera of fossil chambered shells, which, like the Spirula, do not terminate externally in a wide chamber, were probably internal, or partially enclosed shells, serving the office of a float, constructed on the same principles as the float of the Spirula. In the class of fossil shells thus illustrated by the discovery of the animal inclosing the Spirula, we may include the following extinct families, occurring in various positions from the earliest Transition strata to the most recent Secondary formations : — Orthoceratite, Lituite, Baculite, Hamite, Scaphite, Turrilite, Nummulite, Belemnite.

* The uncertainty which has arisen respecting the animal which constructs the Spirula, from the circumstance of the specimen discovered by Peron having been lost, is in some degree removed by Captain King's discovery of another of these shells, attached to a fragment of the mantle of an animal of unknown species resembling a Sepia, which I have seen in the possession of Mr. Owen, at the Royal College of Surgeons, London.

In the genus Lituite, Orthoceratite, and Belemnite, Pl. 44, f. 3, 4, 17, the simple curvature of the transverse plates resembles the character of the Nautilus. In the Baculite, Hamite, Scaphite, and Turrilite, Pl. 44, Fig. 5, 8, 12, 13, 14, 15, the sinuous foldings and foliated edges of the transverse plates resemble those of the Ammonites.

[363 ORTHOCERATITE.]

The Orthoceratites (so called from their usual form, — that of a straight horn) began their existence at the same early period with the Nautili, in the seas which deposited the Transition strata; and are so nearly allied to them in structure, that we may conclude they performed a similar function as floats of Cephalopodous Mollusks. This genus contains many species, which abound in the strata of the Transition series, and is one of those which, having been called into existence amongst the earliest inhabitants of our planet, was at an early period also consigned to almost total destruction.*

An Orthoceratite (see Pl. 44, Fig. 4) is, like the Nautilus, a multilocular shell, having its chambers separated by transverse plates, concave externally, and internally convex; and pierced, either at the centre or towards the margin, by a Siphuncle, (a.) This pipe varies in size, more

* See D'Orbigny's Tableau Méthodique des Céphalopodes. There are, I believe, only two exceptions yet known to the general fact, that the genus Orthoceratite became extinct before the deposition of the Secondary strata had commenced. The most recent rocks in which they have been noticed, are a small and problematical species in the Lias at Lyme, and another species in Alpine Limestone of the Oolite formation, at Halstadt, in the Tyrol.

[364 ORTHOCERATITE.] than that of any other multilocular shell, viz. from one-tenth to one-half of the diameter of the shell; and often assumes a tumid form, which would admit of the distension of a membranous siphon. The base of the shell beyond the last plate presents a swelling cavity, wherein the body of the animal seems to have been partly contained.

The Orthoceratites are straight and conical, and bear the same relation to the Nautili which Baculites (see Pl. 44, Fig. 6) bear to Ammonites; the Orthoceratites, with their simple transverse septa, resembling straight Nautili; and the Baculites, with a sinuous septa, having the appearance of straight Ammonites. They vary considerably in external figure, and also in size; some of the largest species exceeding a yard in length, and half a foot in diameter. A single specimen has been known to contain nearly seventy air chambers. The body of the animal which required so large a float to balance it, must have greatly exceeded, in all its proportions, the most gigantic of our recent Cephalopods; and the vast number of Orthoceratites that are occasionally crowded together in a single block of stone, shows how abundantly they must have swarmed in the waters of the early seas. These shells are found in the greatest numbers in blocks of marble, of a dark red colour from the transition Limestone of Geland, which some

[365 LITUITE . BACULITE.] years ago was imported largely to various parts of Europe for architectural purposes.*

Together with the Orthoceratite, in the Transition Limestone of Oeland, there occurs a cognate genus of Chambered shells, called Lituites. (Pl. 44, Fig. 3.) These are partially coiled up into a spiral form at their smaller extremity, whilst their larger end is continued into a straight tube, of considerable length, separated by transverse plates, concave outwards, and perforated by a siphuncle (a). As these Lituites closely resemble the shell of the recent Spirula (Pl. 44, Fig. 2), their office may have been the same, in the economy of some extinct Cephalopod.
 

As in rocks of the Transition series, the form of a straight Nautilus is presented by the genus

* Part of the pavement in Hampton Court Palace, that of the hall of University College, Oxford, and several tombs of the kings of Poland in the cathedral at Cracow, are formed of this marble, in which many shells of Orthoceratites are discoverable. The largest known species are found in the Carboniferous lime stone of Closeburn, near Edinburgh, being nearly of the size of a man's thigh. The presence of such gigantic Mollusks seems to indicate a highly exalted temperature, in the then existing climate of these northern regions of Europe. See Sowerby's Min. Con. Pl. 246.

[366 BACULITE.] Orthoceratite, so we find in the Cretaceous formation alone, the remains of a genus which may be considered as a straight Ammonite. (See Pl. 44, Fig. 6.)

The Baculite (so called from its resemblance to a straight staff) is a conical, elongated, and symmetrical shell, depressed laterally, and divided into numerous chambers by transverse plates, which, like those in the Ammonite, are sinuous, and terminated by foliated dentations at their junction with the external shell; being thus separated into dorsal, ventral, and lateral lobes and saddles, analogous to those of Ammonites.*

It is curious, that this straight modification of the form of Ammonites should not have appeared, until this Family had arrived at the last stage of the Secondary deposits, throughout which it had occupied so large an extent; and that, after a comparatively short duration, the Baculite should have become extinct, simultaneously with the last of the Ammonites, at the termination of the Chalk formation.

* The external chamber (a) is larger than the rest, and swelling; and capable of containing a considerable portion of the animal. The outer shell was thin, and strengthened, like the Ammonite, by oblique ribs. Near the posterior margin of the shell, the transverse plates are pierced by a Siphuncle (Pl. 44, 5^b, c,). This position of the Siphuncle, and the sinuous form and denticulated edges of the transverse plates, are characters which the Baculite possesses in common with the Ammonite.

[367 HAMITE.] If we imagine a Baculite to be bent round near its centre, until the smaller extremity be came nearly parallel to its larger end, it would present the most simple form of that cognate genus of chambered shells, which, from their frequently assuming this hooked form, have been called Hamites. At Pl. 44, Fig. 9, 11, represent portions of Hamites which have this most simple curvature; other species of this genus have a more tortuous form, and are either closely coiled up, like the small extremity of a Spirula, (Pl. 44, Fig. 2,) or disposed in a more open spiral. (Pl. 44, Fig. 8.)*

It is probable that some of these Hamites

* Both these forms of Hamite bear the same relation to Ammonites that Lituites bear to Nautili; each being nearly such as shells of these genera would respectively present, if partially unrolled. See Phillips' Geol. Yorkshire, Pl. 1, Figs. 22, 29, 30.

Baculites and Hamites have two characters which connect them with Ammonites; first, the position of the Siphuncle, on the back, or outer margin of the shell, (Pl. 44, Figs. 5^b c. 8^a, a. 10. 11, a. 12, a. 13, a.); secondly, the foliated character of the margin of the transverse plates, at their junction with the external shell. (Pl. 44, Fig. 5, 8, 12, 13.) The external shell of Hamites is also fortified by transverse folds or ribs, increasing the strength both of the outer chambers and of the air chambers, upon the same principles that we have pointed out in the case of Ammonites. (See Pl. 44, Fig. 8, 9, 11, 12, 13.)

In certain species of Hamites, as in certain Ammonites, the marginal Siphuncle has a keel-shaped pipe raised over it. Others have a series of spines on each side of the back. (Pl. 44, Fig. 9, 10.)

[368 SCAPHITE.] were partly internal, and partly external shells; where the spines are present, the portion so armed was probably external. Nine species of Hamites occur in the single formation of Gault or Speeton clay immediately below the chalk, near Scarborough. (See Phillips' Geology of Yorkshire.) Some of the larger species equal a man's wrist in diameter.*

The Scaphites constitute a genus of Elliptical chambered shells, (see Pl. 44, Fig. 15, 16,) of remarkable beauty, which are almost peculiar to the Chalk formation; they are so rolled up at each extremity, whilst their central part continues nearly in a horizontal plane, as to resemble the ancient form of a boat; whence the name of Scaphite has been applied to them.

The Hamites grandis, (Sowerby, M. C. 593,) from the Green sand at Hythe, is of these large dimensions.

The inner extremity of the Scaphite is coiled up like that of an Ammonite, (Pl. 44, Fig. 15, c. and Fig. 16) in whorls embracing one another; the last and outer chamber (a) is larger than all the rest together, and is sometimes (probably in the adult state) folded back so as to touch the spire, and thereby materially to contract the mouth, which is narrower than the last or outer chamber. (Pl. 44, Fig. 15, b.) In this character of the external chamber, the Scaphite differs from the Ammonite; in all other respects it essentially agrees with it; its transverse plates being numerous, and pierced by a marginal Siphuncle, at the back of the shell (Fig. 16, a.); and their edges being lobated, deeply cut, and foliated. (Fig. 15, c.)

[369 TURRILITE.] It is remarkable that those approximations to the structure of Ammonites which are presented by Scaphites and Hamites, should have appeared but very rarely, and this in the lias and inferior oolite,* until the period of the cretaceous formations, when the entire type of the ancient and long continued genus Ammonite was about to become extinct.
 

The last genus I shall mention, allied to the family of Ammonites, is composed of spiral shells, of another form, coiled around themselves in the form of a winding tower, gradually diminishing towards the apex (Pl. 44, Fig. 14).

The same essential characters and functions pervade the Turrilites, which we have been tracing in the Scaphites, Hamites, Baculites, and Ammonites. In each of these genera it is the exterior form of the shell that is principally

* The Scaphites bifurcatus occurs in the Lias of Wurtemburg, and Hamites annulatus in the Inferior oolite of France.

The shells of the Turrilites are extremely thin, and their exterior is adorned and strengthened (like that of Ammonites), with ribs and tubercles. In all other respects also, except the manner in which they are coiled up, they resemble Ammonites; their interior being divided into numerous chambers by transverse plates, which are foliated at their edges, and pierced by a siphuncle, near the dorsal margin. (Pl. 44, Fig. 14, a, a.) The outer chamber is large.

[370 UNITY OF DESIGN.]  varied, whilst the interior is similarly constructed in all of them, to act as a float, subservient to the movements of Cephalopodous Mollusks. We have seen that the Ammonites, beginning with the Transition strata, appear in all formations, until the termination of the Chalk, whilst the Hamites and Scaphites are very rare, and the Turrilites and Baculites do not appear at all, until the commencement of the Cretaceous formations. Having thus suddenly appeared, they became as suddenly extinct at the same period with the Ammonites, yielding up their place and office in the economy of nature to a lower order of Carnivorous mollusks in the Tertiary and existing seas.
In the review we have taken of genera in the family of Chambered shells, allied to Nautilus, and Ammonite, we have traced a connected series of delicate and nicely adjusted instruments, adapted to peculiar uses in the economy of every animal to which they were attached. These all attest undeviating Unity of design, pervading many varied adaptations of the same principle; and afford cumulative evidence, not only of the exercise of Intelligence, but also of the same Intelligence through every period of time, in which these extinct races inhabited the ancient deep.

[371 BELEMNITES.]

WE shall conclude our account of chambered shells with a brief notice of Belemnites. This extensive family occurs only in a fossil state, and its range is included within that series of rocks which in our section are called Secondary.* These singular bodies are connected with the other families of fossil chambered shells we have already considered; but differ from them in having their chambers inclosed within a cone-shaped fibrous sheath, the form of which resembles the point of an arrow, and has given origin to the name they bear.

M. de Blainville, in his valuable memoir on Belemnites, (1827) has given a list of ninety-one authors, from Theophrastus downwards, who have written on this subject. The most intelligent among them agree in supposing these bodies to have been formed by Cephalopods allied to the modern Sepia. Voltz, Zieten, Raspail, and Count Münster, have subsequently published important memoirs upon the same subject. The principal English notices on Belemnites are those of Miller, Geol. Trans. N. S.

* The lowest stratum in which Belemnites are said to have been found is the Muschel-kalk, and the highest the upper Chalk of Maestricht.

[372 ITS COMPONENT PARTS.] London, 1826, and that of Sowerby, in his Mim. Conch. vol. vi. p. 169, et seq.

A Belemnite was a compound internal shell, made up of three essential parts, which are rarely found together in perfect preservation.

First, a fibro-calcareous cone-shaped shell, terminating at its larger end in a hollow cone (Pl. 44, Fig. 17. and Pl. 44', Fig. 7, 9, 10, 11, 12).*

Secondly, a conical thin horny sheath, or cup, commencing from the base of the hollow cone of the fibro-calcareous sheath, and enlarging rapidly as it extends outwards to a considerable

* This part of the Belemnite is usually called the sheath, or guard: it is made up of a pile of cones, placed one within an other, having a common axis, and the largest enclosing all the rest. (See Pl. 44, Fig. 17.) These cones are composed of crystalline carbonate of lime, disposed in fibres that radiate from an eccentric axis to the circumference of the Belemnite. The crystalline condition of this shell seems to result from calcareous infiltrations (subsequent to interment), into the intervals between the radiating calcareous fibres of which it was originally composed. The idea that the Belemnite was a heavy solid stony body, whilst it formed part of a living and floating sepia, would be contrary to all analogies afforded by the internal organs of living Cephalopods. The odour, resembling burnt horn, produced on burning this part of a Belemnite, arises from the remains of horny membranes interposed between each successive fibro-calcareous cone.

An argument in favour of the opinion that Belemnites were internal organs, arises from the fact of their surface being often covered with vascular impressions, derived from the mantle in which it was inclosed. In some species of Belemnites the back is granulated, like the back of the internal shell of Sepia officinalis.

[373 CHAMBERED ALVEOLUS.] distance. Pl. 44', Fig. 7, b, e, e', e". This horny cup formed the anterior chamber of the Belemnite, and contained the ink bag, (c), and some other viscera.*

Thirdly, a thin conical internal chambered shell, called the Alveolus, placed within the calcareous hollow cone above described. (Pl. 44, Fig. 17, a. and Pl. 44', Fig. 7, b, b'.)

This chambered portion of the shell is closely allied in form, and in the principles of its construction, both to the Nautilus and Orthoceratite. (See Pl. 44, Fig. 17, a, b. and Fig. 4.) It is divided by thin transverse plates into a series of narrow air-chambers, or areole, resembling a pile of watch-glasses, gradually diminishing towards the apex. The transverse plates are outwardly concave, inwardly convex; and are perforated by a continuous siphuncle, (Pl. 44, Fig. 17, b.), placed on the inferior, or ventral margin.

We have already (Ch. XV. Section II.) described the horny pens and ink-bags of the Loligo, found in the Lias at Lyme Regis. Similar ink-bags have recently been found in connection with Belemnites in the same Lias. Some of these ink-bags are nearly a foot in length, and show

* This laminated horny sheath is rarely preserved in connection with the fibro-calcareous shelly sheath; but in the Lias at Lyme Regis it is frequently found without the shell. Certain portions of it are often highly nacreous, whilst other Parts of the same sheath retain their horny condition.

[374 ANIMAL BELEMNO-SEPTA.] that the Belemuo-sepiæ, from which they were derived, attained great size.

The fact of these animals having been provided with so large a reservoir of ink, affords an à priori probability that they had no external shell; the ink-bag, as far as we yet know, being a provision confined to naked Cephalopods,

In 1829, I communicated to the Geological Society of London a notice respecting the probable connection of Belemnites with certain fossil ink-bags, surrounded by brilliant nacre, found in the Lias at Lyme Regis. (See Phil. Mag. N. S. 1829, p. 388.) At the same time I caused to be prepared the drawings of fossils, engraved in Pl. 44", which induced me to consider these ink-bags as derived from Cephalopods connected with Belemnites. I then withheld their publication, in the hope of discovering certain demonstration, in some specimen that should present these ink-bags in connection with the sheath or body of a Belemnite, and this demonstration has at length been furnished by a discovery made by Professor Agassiz (October, 1834), in the cabinet of Miss Philpotts, at Lyme Regis, of two important specimens, which appear to be decisive of the question. (See Pl. 44', Figs. 7, 9.)

Each of these specimens contains an ink-bag within the anterior portion of the sheath of a perfect Belemnite; and we are henceforth enabled with certainty to refer all species of Belemnites to a family in the class of Cephalopods, for which I would, in concurrence with M. Agassiz, propose the name of Belemno-sepia. Such ink-bags are occasionally found in contact with traces of isolated alveoli of Belemnites: they are more frequently surrounded only by a thin plate of brilliant nacre.

The specimen (Pl. 44", Fig. 1,) was procured by me from Miss Mary Anning in 1829, who considered it as appertaining to a Belemnite. Near its lower end we see the lines of growth of the horny anterior sheath, but no traces of the posterior calcareous sheath; within this horny sheath is placed the ink-bag. The conical form of this anterior chamber seems to have been

[375 INK BAG.] which have not that protection from an external shell, which is afforded by the shell of the N. Pornpilius to its inhabitant, that has no ink-bag. No ink, or ink-bags have been ever seen within the shell of any fossil Nautilus or Ammonite: had such a substance existed in the body of the animals that occupied their outer chamber,

altered by pressure. It is composed of a thin laminated substance (see Pl. 44", Fig. 1, d.), which in some parts is brilliantly nacreous, whilst in other parts it presents simply the appearance of horn. The outer surface of this cup is marked transversely with gentle undulations, which probably indicate stages of growth. Miss Baker has a Belemnite from the inferior Oolite near Northampton, in which one half of the fibrous cup being removed, the structure of the conical shell of the alveolus is seen impressed on a cast of iron-stone, and exhibits undulating lines of growth, like those on the exterior of the shell of N. Pornpilius.

M. Blainville, although he had not seen a specimen of Belemnite in which the anterior horny conical chamber is preserved, has argued from the analogy of other cognate chambered shells that such an appendage was appertinent to this shell. The soundness of his reasoning is confirmed by the discovery of the specimen before us, containing this part in the form and place which he had predicted. " Par analogie elle était donc évidemment dorsale et terminale, et lorsqu'elle était complète, c'est-à-dire pourvue d'une cavité, l'extremité postérieure des viscères de l'animal (très-probablement l'organe sécréteur de la génération et partie du foie) y était renfermée." — Blainville Mém. sur les Bèlemnites. 1827 . Page 28.

Count Munster (Mem. Geol. par A. Boue, 1832, V. 1, Pl. 4, Figs. 1, 2, 3, 15) has published figures of very perfect Belemnites from Solenhofen, in some of which the anterior horny sheath is preserved, to a distance equal to the length of the solid calcareous portion of the Belemnite (Pl. 44', Figs. 10, 11, 12, 13), but in neither of these are there any traces of an ink-bag.

[376 CAUSES OF PARTIAL PRESERVATION.] some traces of it must have remained in those beds of has at Lyme Regis, which are loaded with Nautili and Ammonites, and have preserved the ink of naked Cephalopods in so perfect a condition. The young Sepia officinalis, whilst included within the transparent egg, exhibits its ink-bag distended with ink, provided before-hand for use as soon as it is excluded; and this ink-bag is surrounded by a covering of brilliant nacreous matter, similar to that we find on certain internal membranes of many fishes.*

* I would here add a few words in explanation of the curious fact, that among the innumerable specimens of Belemnites which have so long attracted the attention of naturalists, not one has till now been found entire in all its parts, having the ink within its external chamber; either the fibro-calcareous sheath is found detached from the horny sheath and ink-bag, or the ink-bag is found apart from the Belemnite, and surrounded only by the nacreous horny membrane of its anterior chamber. We know from the condition of the compressed nacreous Ammonites in the Las-shale at Watchet, that the nacreous lining only of these shells is here preserved, whilst the shell itself has perished. This fact seems to explain the absence of the calcareous sheath and shell in almost every specimen of ink-bags at Lyme Regis, which is surrounded with iridescent nacre, like that of the Ammonites of Watchet. The matrix in these cases may have had a capacity for preserving nacreous or horny substances, whilst it allowed the more soluble calcareous matter of shells to be removed, probably dissolved in some acid.

The greater difficulty is to explain the reason, why amidst the millions of Belemnites that are dispersed indiscriminately through almost all strata of the Secondary series, and sometimes form entire pavements in beds of shale connected with the Lias and Inferior oolite, it so rarely happens that either the horny sheath, or the ink-bag, have been preserved. We may, 1 think, explain

[377 BELEMNITE COMPARED WITH NAUTILUS.] Comparing the shell of Belemnite, with that of Nautilus, we find the agreement of all their

the absence of the nacreous horny sheath, by supposing that a condition of the matrix favourable to the preservation of the calcareous sheath was unfavourable to the preservation of horny membrane; and we may also explain the absence of ink-bags, by supposing that the decomposition of the soft parts of the animal usually caused the ink to be dispersed, before the body was buried in the earthy sediment then going on.

At the base of Golden Cap hill, near Charmouth, the shore presents two strata of marl almost paved with Belemnites, and separated by about three feet only of comparatively barren marl. As great numbers of these Belemnites have Serpulæ, and other extraneous shells attached to them, we learn from this circumstance that the bodies and ink-bags had decomposed, and the Belemnites lain some time uncovered at the bottom. These facts are explained by supposing that the sea near the spot was much frequented by Belemno-sepiæ during the intervals of the deposition of the Lias. Similar conclusions follow, from the state of many Belemnites in the chalk of Antrim, which had been perforated by small boring animals, whilst they lay at the bottom of the sea, and these perforations filled with casts of chalk or flint, when the matter of the chalk strata was deposited upon them, in a soft and fluid state. (See Allan's Paper on Belemnite, Trans. Royal Soc. Edin., and Miller's Paper, Geol. Trans. Lond. 1826, p. 53.)

Thus of the millions of Belemnites which crowd the Secondary formations, only the fibro-calcarcous sheath and chambered alveoli are usually preserved; whilst in certain shale beds this sheath and shell have sometimes entirely disappeared, and the horny or nacreous sheath and ink-bag alone remain. See Pl. 44", Fig. 1, 2., 3, 4, 5, 6, 7, 8. In the rare case, Pl. 44', Fig. 7, which has afforded the clue to this hitherto unexplained enigma, we have all the three essential parts of a Belemnite preserved in their respective places nearly entire. The ink-bag (c) is placed within the anterior horny cup (e, e', e"); and the chambered alveolus (b b') within the hollow cone of the posterior fibro calcareous shell, or common Belemnite.

[378 ANALOGIES.] most important parts to be nearly complete ;* and the same analogies might be traced through the other genera of chambered shells.

* The air chambers and siphuncle are, in both these families, essentially the same.

In Belemnites, the anterior extremity of the fibro-calcareous shell, which forms a hollow straight cone, surrounding the transverse plates of the chambered alveolus, represents the hollow coiled-up cone containing all the transverse plates, which make up the alveolus of the Nautilus.

The anterior horny cup, or outer chamber of the Belemnite, surrounding the ink-bag, and other viscera, represents the large anterior shelly chamber which contains the body of the Nautilus.

The posterior portion of the Belemnite, which is elongated backwards into a fibrous pointed shaft, is a modification of the apex of the straight cone of this shell, to which there seems to be no equivalent in the apex of the coiled-up cone of Nautilus. The cause of this peculiar addition to the ordinary parts of shells, seems to rest in the peculiar uses of the shaft of the Belemnite, as an internal shell, acting like the internal shell of the Sepia Officinalis, to support the soft parts of the animals, within the bodies of which they were respectively enclosed. The fibrous structure of this shaft is such as is common to many shells, and is most obvious in the Pinnæ.

Comparing the Belemnite, or internal shell of Belemno sepia with the Sepiostaire, (Blainville), or internal shell of the Sepia Officinalis, we have the following analogies. In the Sepiostaire, (Pl. 44', Fig. 2, a. e. and Figs. 4, 4', 5), the small conical apex (a) represents the apex of the long calcareous posterior sheath of the Belemnite, (Fig. 7, a.) and the calcareous plates, alternating with horny plates, which form the shield and shallow cup of the Sepiostaire, (Pl. 44', Fig. 2, e. and Fig. 5. e.), represent the hollow fibro-calcareous cone or cup of the Belemnite, surrounding its alveolus.

The margin of the horny plates, interposed between the calcareous plates of the shield and cup of the Sepiostaire, (Pl. 44', Fig. 4, e, e, e', e'.), represents the horny marginal cavity of the

[379 NUMBER OF SPECIES.] Eighty-eight species of Belemnites have al ready been discovered;* and the vast numerical amount to which individuals of these species were extended, is proved by the myriads of their fossil remains that fill the Gohitic and Cretaceous formations. When we recollect that throughout both these great formations, the still more numerous extinct family of Aminonites is co-extensive with the Belemnites; and that each species of Arumonite exhibits also contrivances, more complex and perfect than those retained in the few

cone of the Belemnite, beyond the base of its hollow calcareous cone, (Pl. 44', Fig. 7, e. e'. e"). This horny sheath of the Belemnite was probably formed by the prolongation of the horny larninæ which were interposed between its successive cones of fibro-calcareous matter.

The chambered alveolus of the Belemnite is represented by the congeries of thin transverse plates, (Pl. 44', Fig. 4, b.) which occupy the interior of the shallow cup of Sepiostaire, (e. e'.); these plates are composed of horny matter, penetrated with carbonate of lime.

The hollow spaces between them, (Fig. 5, b, b',), which are nearly a hundred in number in the full grown animal, act as air chambers to make the entire shell permanently lighter than water; but there is no siphuncle to vary the specific gravity of this shell; and the thin chambers between its transverse plates are studded with an infinity of minute columnar, and sinuous partitions, planted at right angles to the plates, and giving them support. (Fig. 6', 6", 6"').

The absence of a siphuncle renders the Sepiostaire an organ of more simple structure, and of lower office, than the more compound shell of Belemnite.

* (See index to M. Brochant de Villiers' Translation of De la Beche's Manual of Geology).

[380 AFFINITIES OF CHAMBERED SHELLS.] existing cognate genera of Cephalopods; we cannot but infer that these extinct families filled a larger space, and performed more important functions among the inhabitants of the ancient seas, than are assigned to their few living representatives in our modern oceans.

It results from the view we have taken of the zoological affinities between living and extinct species of chambered shells, that they are all connected by one plan of organization; each forming a link in the common chain, which unites existing species with those that prevailed among the earliest conditions of life upon our globe; and all attesting the Identity of the design, that has effected so many similar ends through such a variety of instruments, the principle of whose construction is, in every species, fundamentally the same.

Throughout the various living and extinct genera of Chambered shells, the use of the air chambers and siphon, to adjust the specific gravity of the animals in rising and sinking, appears to have been identical. The addition of a new transverse plate within the conical shell added a new air chamber, larger than the preceding one, to counterbalance the increase of weight that attended the growth of the shell and body of all these animals.

[381 NATURAL HYDRAULIC INSTRUMENTS] These beautiful arrangements are, and ever have been, subservient to a common object, viz. the construction of hydraulic instruments of essential importance in the economy of creatures destined to move sometimes at the bottom, and at other times upon or near the surface of the sea. The delicate adjustments whereby the same principle is extended through so many grades and modifications of a single type, show the uniform and constant agency of some controlling Intelligence; and in searching for the origin of so much method and regularity amidst variety, the mind can only rest, when it has passed back, through the subordinate series of Second causes, to that great First Cause, which is found in the will and power of a common Creator.
 

IF the present were a fit occasion for such minute inquiries, the investigations of the various known species of Microscopic shells would unfold a series of contrivances having relation to the economy of the minute Cephalopods by which they were constructed, not less striking than those we have been examining in the shells of extinct

[382 MINUTE MULTILOCULAR SHELLS.] Genera and species of larger Cephalopods. M. D'Orbigny has noticed from 600 to 700 species of these shells, and has prepared magnified models of 100 species, comprehending all the Genera.*

The greater number of these shells are microscopic, and swarm in the Mediterranean and Adriatic. Their fossil species abound chiefly in the Tertiary formations, and have hitherto been noticed principally in Italy. (See Soldani, as quoted at page 117 of this volume.) They occur also in the Chalk of Meudon, in the Jura Limestone of the Charente inferieure, and the Oolite of Calne. They have been found by the Marquis of Northampton in Chalk flints from the neighbourhood of Brighton.

* M. D'Orbigny, in his Classification of the shells of Cephalopodous Mollusks, has established three orders. 1 . Those that have but a single chamber, like the shell of the sepia and horny pen of the Loligo. 2. Polythalamous shells, which have a siphuncle passing through all the internal chambers, and which terminate in a large external chamber, beyond the last partition, such as Nautili, Ammonites, and Belemnites. 3. Polythalamous internal shells, which have no chamber beyond their last partition.

Shells of this Order have no siphuncle, but the chambers communicate with each other by means of one or many small foramina. On this distinctmon he has founded his Order Foraminiferes, containing five families and fifty-two genera.

It may be necessary to apprize the reader that doubts have been entertained as to the cephalopodous structure of some of these minute multilocular shells; and that there are not wanting those who attribute to them a different organization.

[383 NUMMULITE.] The Nummulite is the only Genus I shall select on the present occasion from this Order. It is included in M. D'Orbigny's Section Nautiloids.

Nummulites (Pl. 44, Fig. 6, 7,) are so called from their resemblance to a piece of money, they vary in size from that of a crown piece to microscopic littleness; and occupy an important place in the history of fossil shells, on account of the prodigious extent to which they are accumulated in the later members of the Secondary, and in many of the Tertiary strata. They are often piled on each other nearly in as close contact as the grains in a heap of corn. In this state they form a considerable portion of the entire bulk of many extensive mountains, e. g. in the Tertiary limestones of Verona and Monte Bolca, and in secondary strata of the Cretaceous formation in the Alps, Carpathians, and Pyrenees. Some of the pyramids, and the Sphinx, of Egypt are composed of limestone loaded with Nummulites.

It is impossible to see such mountain-masses of the remains of a single family of shells thus added to the solid materials of the globe, without recollecting that each individual shell once held an important place within the body of a living animal; and thus recalling our imagination to those distant epochs when the waters of the ocean which then covered Europe were filled

[384 NUMMULITE.] with floating swarms of these extinct Mollusks, thick as the countless myriads of Beröe and Clio Borealis that now crowd the waters of the polar seas.*

The Numrnulites, like the Nautilus and Ammonite, are divided into air chambers, which served the office of a float; but there is no enlargement of the last chamber which could have contained any part of the body of the animal. The chambers are very numerous, and minutely divided by transverse plates; but are without a

* We have an analogy to this supposed state of crowded population of Nummulites in the ancient sea, in the marvellous fecundity of the northern ocean at the present time. It is stated by Cuvier, in his memoir on the Clio Borealis, that in calm weather, the surface of the water in these seas swarms with such millions of these mollusks (rising for a moment to the air at the surface, and again instantly sinking towards the bottom), that the whales can scarce open their enormous mouths without gulping in thousands of these little gelatinous creatures, an inch long, which, together with Medusæ, and some smaller animals, constitute the chief articles of their food; and we have a farther analogy in the fact mentioned in Jameson's Journal, vol. ii. p. 12. " That the number of small Medusæ in some parts of the Greenland seas is so great, that in a cubic inch, taken up at random, there are no less than 64. In a cubic foot this will amount to 110,592; and in a cubic mile (and there can be no doubt of the water being charged with them to that extent), the number is such, that allowing one person to count a million in a week, it would have required 80,000 persons, from the creation of the world, to complete the enumeration." — See Dr. Kidd's admirable Introductory Lecture to a course of Comparative Anatomy, Oxford, 1824, p. 35.

[385 NUMMULITE.] siphuncle.* The form of the essential parts varies in each species of this genus, but their principles of construction, and manner of operation, appear in all to have been the same.

The remains of Nummulites are not the only animal bodies which have contributed to form the calcareous strata of the crust of the earth; other, and more minute species of Chambered shells have also produced great, and most surprising effects. Lamarck (Note, v. 7. p. 611), speaking of the Miliola, a small multiocular shell, no larger than a millet seed, with which the strata of many quarries in the neighbourhood of Paris are largely interspersed, notices the important influence which these minute bodies have exercised by reason of their numerical abundance. We scarcely condescend, says he, to examine microscopic shells, from their insignificant size; but we cease to think them insignificant, when we reflect that it is by means of the smallest objects, that Nature every where produces her most remarkable and astonishing phenomena. Whatever she may seem to lose in point of volume in the production of living bodies, is amply made up by the number of the individuals, which she multiplies with admirable

* In Pl. 44, Figs. 6, 7, sections of two species of Nummulite are copied from Parkinson. These show the manner in which the whorls are coiled up round each other, and divided by oblique septa.

[386] promptitude to infinity. The remains of such minute animals have added much more to the mass of materials which compose the exterior crust of the globe, than the bones of Elephants, Hippopotami, and Whales.