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the small intestine, we have additional evidence to show even the form of the minute vessels and folds of the mucous membrane, by which it was lined. This evidence consists in a series of vascular impressions and corrugations on the surface of the Coprolite, which it could only have received during its passage through the windings of this flat tube.* Specimens thus marked are engraved at PI. 15, Figs, 3, 5, 7, 10, 12, 13, 14.

If we attempt to discover a final cause for these curious provisions in the bowels of the extinct reptile inhabitants of the seas of a former world, we shall find it to be the same that explains the existence of a similar structure in the modern voracious tribes of Sharks and Dog-fish.f

As the peculiar voracity of all these animals required the stomach to be both large and long, there would remain but little space for the smaller viscera; these are therefore reduced, as we have seen, nearly to the state of a flattened tube, coiled like a corkscrew around itself; their bulk is thus materially diminished, whilst the amount of absorbing the bodies of several species of fossil fish, from the lias at Lyme Regis. Dr. Hibbert has shown that the strata of fresh-water limestone, in the lower region of the coal formation, at Burdie House, near Edinburgh, are abundantly interspersed with Coprolites, derived from fishes of that early era; and Sir Philip Egerton has found similar fcecal remains, mixed with scales of the Megalichthys, and freshwater shells, in the coal formation of Newcastle-underLyne. In 1832, Mr. W. C. Trevelyan recognised Coprolites in the centre of nodules of clay ironstone, that abound in a low cliff composed of shale, belonging to the coal formation at Newhaven, near Leith. I visited the spot, with this gentleman and Lord Greenock, in September, 1834, and found these nodules strewed so thickly upon the shore that a few minutes sufficed to collect more specimens than I could carry; many of these contained a fossil fish, or fragment of a plant, but the greater number had for their nucleus, a Coprolite, exhibiting an internal spiral structure; they were probably derived from voracious fishes, whose bones are found in the same stratum. These nodules take a beautiful polish, and have been applied by the lapidaries of Edinburgh to make tables, letter presses, and ladies' ornaments, under the name of Beetle stones, from their supposed insect origin. Lord Greenock has discovered, between the laminae of a block of coal, from the neighbourhood of Edinburgh, a mass of petrified intestines distended with Coprolite, and surrounded with the scales of a fish, which Professor Agassiz refers to the Megalichthys.

* These impressions cannot have been derived from the membrane of the inferior large intestine, because they are continued along those surfaces of the inner coils of the Coprolite, which became permanently covered by its outer coils, in the act of passing from the spiral tube into this large intestine.

t Paley, in his chapter on mechanical compensations on the structure of animals, mentions a contrivance similar to that which we attribute to the Ichthyosaurus, as existing in a species of Shark, (the Alopecias, Squalus Vulpes, or Sea Fox.) "In this animal, he says, the intestine is straight from one end to the other: but, in this straight, and consequently short intestine, is a winding, cork-screw, spiral passage, through which the food, not without several circumvolutions, and in fact by a long route, is conducted to its exit. Here the shortness of the gut is compensated by the obliquity of the perforation."

Dr. Fitton has called my attention to a passage in Lord King's Life of Locke, 4°. p. 166, 167, from which it appears that the importance of a spiral disposition within the intestinal canal, which he observed in many preparations in the collection of anatomy at Leyden, was duly appreciated by that profound philosopher.

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This distinguished naturalist has recently ascertained that the fossil worm-like bodies, so abundant in the lithographic slate of Solenhofen, and described by Count Mlinster in the Petrefacten of Goldfuss, under the name of Lumbricaria, are either the petrified intestines of fishes, or the contents of their intestines, still retaining the form of the tortuous tube in which they were lodged. To these remarkable fossils he has given the name of Cololites. (PI. 15', is copied from one of a series that are engraved in Goldfuss. Petrefacten, PI. 66.) He has also found similar tortuous petrifactions within the abdominal cavity of fossil fishes, belonging to several species of the genus Thrissops and Leptolepis, occupying the ordinary position of the intestines between the ribs.* (See Agassiz Poissons Fossiles, liv. 2, Appendix, p. 15.)

that the form of the Coprolites within the Maeropoma most nearly resemble those engraved, PI. 15, Figs. 8, 9, of the present work: he also conjectures that the more tortuous kinds, (PI. 15, Figs. 5, 7,) long known by the name of Juli, and supposed to be fossil fir cones, may have been derived from fishes of the Shark family, (Ptychodus) whose large palatal teeth (PI. 27./) abound in the same localities of the chalk formation with them, at Steyningand Hamsey.

It is probable that to many persons inexperienced in anatomy, any kind of information on a subject so remote, and apparently so inaccessible, as the intestinal structure of an extinct reptile or fossil fish, may at first appear devoid of the smallest possible importance; but it assumes a character of high value, in the investigation of the proofs of creative wisdom and design, that are unfolded by the researches of Geology; and supplies a new link to that important chain, which connects the lost races that formerly inhabited our planet, with a species that are actually living and moving around ourselves.* The systematic recurrence, in animals of such distant eras, of the same contrivances, similarly disposed to effect similar purposes, with analogous adaptations to peculiar conditions of existence, shows that they all originated in the same Intelligence.

* As these Cololites are most frequently found insulated in the lithographic limestone, M. Agassiz has ingeniously explained this fact by observing the process of decomposition of dead fishes in the lakes of Switzerland. The dead fish floats on the surface with its belly upwards, until the abdomen is so distended with putrid gas, that it bursts: through the aperture thus formed the bowels come forth into the water, still adhering together in their natural state of convolution. This intestinal mass is soon torn from the body by the movement of the waves; the fish then sinks, and the bowels continue a long time floating on the water: if cast on shore, they remain many days upon the sand before they are completely decomposed. The small bowels only are thus detached from the body, the stomach and other viscera remain within it.

We owe this illustration of the nature of these fossil bodies, whose origin has hitherto been inexplicable, to the author of a most important work on fossil fishes, now under publication at Neuchatel. His qualifications for so great and difficult a task arc abundantly guaranteed by the fact, that Cuvier, on seeing the progress he had made, at once placed at the disposal of Professor Agassiz the materials he had himself collected towards a similar work.

When we see the body of an Ichthyosaurus, still containing the food it had eaten just before its death, and its ribs still surrounding the remains of fishes, that were swallowed ten thousand, or more than ten times ten thousand years ago, all these vast intervals seem annihilated, time altogether disappears, and we are almost brought into as immediate contact with events of immeasurably distant periods, as with the affairs of yesterday.

SECTION VI.

PLESIOSAURUS.f

We come next to consider a genus' of extinct animals, nearly allied in structure to the Ichthyosaurus, and co-extensive with it through the middle age of our terrestrial history. The discovery of this genus forms one of the most important additions that Geology has made to comparative

* Le temps qui repand de la dignite sur tout ce qui echappe ii son pouvoir deslructeur, fait voir ici un exemple singulier de son influence: ces substances si vilcs dans lcur origine, ctant rcndues a. la lumiere apres tant de siecles, deviennent d'une grande importance puis qu'clles servent a remplir un nouveau chapitre dans l'histoire naturclle du globe.—Bulletin Soc. Imp. do Moscow, No. VI. 1833, p. 23.

t See PI. 16, 17, 18, 19.

VOL. Ik 14.

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