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have farther evidence to show, that in times anterior to, and during the deposition of the Chalk, the same important functions were consigned to other carnivorous Mollusks, viz. the Testaceous Cephalopods ;* these are of comparatively rare occurrence in the Tertiary strata, and in our modern seas; but, throughout the Secondary and Transition formations, where carnivorous Trachelipods are either wholly wanting, or extremely scarce, we find abundant remains of carnivorous Cephalopods, consisting of the chambered shells of Nautili and Ammonites, and many kindred extinct genera of polythalamous shells of extraordinary beauty. The Molluscous inhabitants of all these chambered shells, probably possessed the voracious habits of the modern Cuttle Fish, and by feeding like them upon young Testacea and Crustacea, restricted the excessive increase of animal life at the bottom of the more ancient seas. Their sudden and nearly total disappearance at the commencement of the Tertiary era, would have caused a blank in the " police of nature," allowing the herbivorous tribes to increase to an excess, that would ultimately have been destructive of marine vegetation, as well as of themselves, had they not been replaced by a different order of carnivorous creatures, destined to perform in another manner, the office which the inhabitants of Ammonites and various extinct genera of chambered shells then ceased to discharge. From that time onwards, we have evidence of the abundance of carnivorous Trachelipodes, and we see good reason to adopt the conclusion of Mr. Dillwyn, that " in the formations above the Chalk, the vast and sudden decrease of one predaceous tribe has been provided for by the creation of many new genera, and species, possessed of similar appetencies, and yet formed for obtaining their prey by habits entirely different from those of the Cephalopods."!
* See explanation of the term Cephalopod, in note at p. 230.
t Mr. Dillwyn observes farther, that all the herbivorous marine Cepha
The design of the Creator seems at all times to have been, to fill the waters of the seas, and cover the surface of the earth with the greatest possible amount of organized beings enjoying life; and the same expedient of adapting the vegetable kingdom to become the basis of the life of animals, and of multiplying largely the amount of animal existence by the addition of Carnivora to the Herbivora, appears to have prevailed from the first commencement of organic life unto the present hour.
Mr. De la Beche has recently published a list of the specific gravities of living shells of different genera, from which he shows that their weight and strength are varied in ac commodation to the habits and habitation of the animals by which they are respectively constructed; and points out evidence of design, such as we discover, in all carefully conducted investigations of the works of nature, whether among the existing or extinct forms of the animal creation.*
lopods of the Transition and Secondary strata were furnished with an operculum, as if to protect them against the carnivorous Cephalopods which then prevailed abundantly; but that in the Tertiary formations, numerous herbivorous genera appear, which are not furnished with opercula, as if no longer requiring the protection of such a shield, after the extinction of the Ammonites and of many cognate genera of carnivorous Trachelipods, at the termination of the Secondary period, i. e. after the deposition of the Chalk formation.
* "It can scarcely escape the observation of the reader, that, while the specific gravities of the land shells enumerated are generally greatest, the densities of the floating marine shells are much the smallest. The design of the difference is obvious: The land shells have to contend with all changes of climate, and to resist the action of the atmosphere, while, at the same time, they are thin for the purpose of easy transport, their density is therefore greatest. The Argonaut, Nautilus, and creatures of the like habits require as light shells as may be consistent with the requisite strength; the relative specific gravity of such shells is consequently small. The greatest observed density was that of a Helix, the smallest, that of an Argonaut. The shell of the Ianthina, a floating Molluscous creature, is among the smallest densities. The specific gravity of all the land shells examined was greater than that of Carara marble; in general more approaching to Arragonite. The fresh-water and marine shells, with the exception of the Vol. i.—20
FOSSIL REMAINS OF NAKED MOLLUSKS, PENS, AND INK-BAGS OF" LOLIGO.
It is well known that the common Cuttle Fish, and other living species of Cephalopods,* which have no external shell, are protected from their enemies by a peculiar internal provision, consisting of a bladder-shaped sac, containing a black and viscid ink, the ejection of which defends them, by rendering opaque the water in which they thus become concealed. The most familiar examples of this contrivance are found in the Sepia vulgaris, and Loligo of our own seas. (See PI. 28, Fig. 1.)
It was hardly to be expected that we should find, amid the petrified remains of animals of the ancient world, (remains which have been buried for countless centuries in the deep foundations of the earth,) traces of so delicate a fluid as the ink which was contained within the bodies of extinct species of Cephalopods, that perished at periods so incalculably remote; yet the preservation of this substance is estaWished beyond the possibility of doubt, by the recent discovery of numerous specimens in the Lias of Lyme Regis,* in which the ink-bags are preserved in a fossil state, still distended, as when they formed parts of the organization of living bodies, and retaining the same juxta-position to an internal rudimentary shell resembling a horny pen, which the ink-bag of the existing Loligo bears to the pen within the body of that animal. (PI. 28, Fig. 1.)
Argonaut, Nautilus, Ianthina, Lithodomus, Haliotis, and great radiated crystalline Teredo from the East Indies, exceeded Carara marble in density. This marble and the Haliotis are of equal specific gravities."—De la Beche's Geological Researches, 1834, p. 76.
* The figure of the common Calmar, or Squid (Loligo Vulgaris Lam. —Sepia loligo of Linnaeus,) see PL 28, Fig. 1, illustrates the origin of the term Cephalopod, a term applied to a large family of molluscous animals, from the fact of their feet being placed around their heads. The feet are lined internally with ranges of horny cups, or suckers, by which the animal seizes on its prey, and adheres to extraneous bodies. The mouth, in form and substance resembles a Parrot's beak, and is surrounded by the feet. By means of these feet and suckers the Sepia octopus, or common Poulpe (the Polypus of the ancients,) crawls with its head downwards, along the bottom of the sea.
Having before us the fact of the preservation of this fossil ink, we find a ready explanation of it, in the indestructible nature of the carbon of which it was chiefly composed. Cuvier describes the ink of the recent Cuttle Fish, as being a dense fluid of the consistence of pap, " bouillie," suspended in the cells of a thin net-work that pervades the interior of the ink-bag; it very much resembles common printers' ink. A substance of this nature would readily be transferred to a fossil state, without much diminution of its bulk.f
PI. 28, Fig. 5, represents an ink-bag of a recent Cuttle Fish, in which the ink is preserved in a desiccated state, being not much diminished from its original volume. Its form is similar to that of many fossil ink-bags (PL 29, Figs. 3—10,) and the indurated ink within it differs only from the fossil ink, inasmuch as the latter is impregnated with carbonate of lime.
* We owe this discovery to the industry and skill of Miss Mary Anning, to whom the scientific world is largely indebted, for having brought to light so many interesting remains of fossil Reptiles from the Lias at Lyme Regis.
t So completely are the character and qualities of the ink retained in its fossil state, that when, in 1826,1 submitted a portion of it to my friend Sir Francis Chantrcy, requesting him to try its power as a pigment, and he had prepared a drawing with a triturated portion of this fossil substance; the drawing was shown to a celebrated painter, without any information as to its origin, and he immediately pronounced it to be tinted with sepia of excellent quality, and begged to be informed by what colourman it was prepared. The common sepia used in drawing is from the ink-bag of an oriental species of cuttle-fish. The ink of the cuttle-fishes, in its natural state, is said to be soluble only in water, through which it diffuses itself instantaneously; being thus remarkably adapted to its peculiar service in the only fluid wherein it is naturally employed.
In a communication to the Geological Society, February 1829, I announced that these fossil ink-bags had been discovered in the Lias at Lyme Regis, in connexion with horny bodies, resembling the pen of a recent Loligo.
These fossil pens are without any trace of nacre, and are composed of a thin, laminated, semi-transparent substance, resembling horn. Their state of preservation is such as to admit of a minute comparison of their internal structure with that of the pen of the recent Loligo; and leads to the same result which we have collected from the examination of so many other examples of fossil organic remains; namely, that although fossil species usually differ from their living representatives, still the same principles of construction have prevailed through every cognate genus, and often also through the entire families under which these genera are comprehended.
The petrified remains of fossil Loligo, therefore, add another link to the chain of argument which we are pursuing, and aid us in connecting successive systems of creation which have followed each other upon our Planet, as parts of one grand and uniform Design. Thus the union of a bag of ink with an organ resembling a pen in the recent Loligo, is a peculiar and striking association of contrivances, affording compensation for the deficiency of an external shell, to an animal much exposed to destruction from its fellowtenants of the deep; we find a similar association of the same organs in the petrified remains of extinct species of the same family, that are preserved in the ancient marl and limestone strata of the Lias. Cuvier drew his figures of the recent Sepia with ink extracted from its own body. I have drawings of the remains of extinet species prepared also with their own ink: with this fossil ink I might record the fact, and explain the causes of its wonderful preservation. I might register the proofs of instantaneous death detected