« AnteriorContinuar »
As far as we can argue from the analogy of living species, the presence of large Scorpions is a certain index of the warmth of the climate in which they lived; and this indication is in perfect harmony with those afforded by the tropical aspect of the vegetables with which the Scorpion, found in the Bohemian coal-field, is associated.
Fourth Class of Articulated An hnals.
Although the numerical amount of living Insects formsso vast a majority of the inhabitants of the present land, few traces of this large class of Articulated animals have yet been discovered in a fossil state. This may probably result from the circumstance, that the greatest portion of fossil animal remains are derived from the inhabitants of salt water,. a medium in which only one or two species of Insects are now supposed to live.
racteristic pincers on the right claw. Between this claw and the tail lies a fossil carbonized Seed, of a species common in the Coal formation.
The horny covering of this Scorpion is in a most extraordinary state of preservation, being neither decomposed nor carbonized. The peculiar substance (Chitinc or Elytrine) of which, like the elytra of Beetles, it is probably composed, has resisted decomposition and mineralization. It can readily be stripped off, is elastic, translucent, and horny. It consists of two' layers, both retaining their texture. The uppermost of these (PI. 46', Fig. 6. a.),is harsh, almost opaque, of a dark-brown colour, and flexible; the under skin (PI. 46', Fig. 6. b.) is tender, yellow, less~ elastic, and organized like the upper. The structure of both exhibits, under the microscope, hexagonal cells, divided by strong partitions. Both are penetrated at intervals by pores, which are still open, each having a sunk areola, with a minute opening at its centre for the orifices of the trachea. Fig. 7. rcpre--' sents impressions of tho muscular fibres connected with the movement of' the legs.
* See PL 46". Figs. 1. 2. (t 4—11.
Had no indications of Insects been discovered in a fossil state, the presence in any strata, of Scorpions or Spiders botli belonging to families constructed to feed on Insects, would have afforded a strong ii priori argument, in favour of the probability, of the contemporaneous existence of that very numerous class of animals, which now forms the prey of the Arachnidans. This probability has been recently confirmed by the discovery of two Coleoptera of the family Curculionidae in the Iron-stone of Coalbrook Dale,* and also of the wing of a Corydalis, which will be noticed in our description of PI. 46".
It is very interesting and important, to have discovered in the Coal formation fossil remains, which establish the existence of the great Insectivorous Class Arachnidans, at this early period. It is no less important to have found also in the same formation the remains of Insects, which may have formed their prey. Had neither of these discoveries been made, the abundance of Land plants would have implied the probable abundance of Insects, and this probability would have involved also that of the contemporaneous existence of Arachnidans, to control their undue increase. All these probabilities are now reduced to certainty, and we are thus enabled to fill up what has hitherto appeared a blank in the history of animal life, from those very distant times when the Carboniferous strata were deposited.
The Estuary, or Fresh-water formation of those strata of the Corboniferous series which contain shells of Unio, in Coalbrook Dale, and in other Coal basins, renders the presence of Insects and Arachnidans in such strata, easy of explanation; they may have been drifted from adjacent
• Our figures (PI. 46". Figs, 1. 2.) represent these fossils of their natural size. See description of this Plate for farther details respecting them.
310 INSECTS IN SECONDARY AND TERTIARY STRATA.
lands, by the same torrents that transported the terrestrial vegetables which have produced the beds of Coal.
The existence of the wing-covers of insects in the Secondary Series, in the Oolitic slate of Stonesfield, has been long known; these are all Coleopterous, and in the opinion of Mr. Curtis many of them approach most nearly to the Buprestis, a genus now most abundant in warm latitudes. (See PI. 46''. Figs. 4. 5. 6. 7. 8. 9. 10.*)
Count Munster has in his collection twenty-five species of fossil insects, found in the Jurassic Limestone of Solenhofen; among these are five species of the existing Family of Libellula, (See PI. 1, Fig. 49,) a large Ranatra, and several Coleoptera.
- Numerous fossil Insects have recently been discovered in the Tertiary Gypsum of Fresh-water formation at Aix, in Provence. M. Marcel de Serres speaks of sixty-two Genera, chiefly of the Orders Diptera, Hemiptera, and Coleoptera: and Mr. Curtis refers all the specimens he has seen from Aix to European forms, and most of them to existing Genera.f Insects occur also in the tertiary Brown coal of Orsberg on the Rhine.
* M.Aug. Odier has ascertained, that the Elytra and other part3 of the horny covering of insects, contain the peculiar substance Chitine or Elytrine, which approaches nearly to the vegetable principle Lignine; these parts of insects burn without fusion, or swelling, like horn, and without the smell of animal matter; they also leave a Coal which retains their form.
M. Odier found that even the hairs of a Scarabaus nasicornis retained their form after burning, and therefore concludes that they are different from the hairs of vertebral animals. This circumstance explains the preservation of the hairs on the horny cover of the Bohemian Scorpion.
He ascertained also that the Sinews (Nervures) of Scarabaei, are composed of Chitine, and that the soft flexible laminae'of the shell of a crab, which remain after the separation of the Lime, also contain Chitine.
Cuvier observes, that the Integuments of Entomostracons, are rather horny than calcareous, and that in this respect they approximate to the nature of Insects and Arachnidans. See Zoological Journal. London, 1825, vol. i. p.
f See Edinburgh New Phil. Journ. Oct. 1829.
We have seen from the examples cited in the last four sections, that all of the four existing great Classes of the grand Division of Articulated animals, viz. Annelidans, Crustaceans, Arachnidans, and Insects, and many of their Orders, had entered on their respective functions in the natural world, at the early epoch of the Transition formations. We find evidences of change in the Families of these Orders, at several periods of the Secondary and Tertiary series, very distant from one another; and we farther find each Family variously represented during different intervals by Genera, some of which are known only in a fossil state, whilst others (and these chiefly in the lower Classes, have extended through all geological Eras unto the present time.
On these facts we may found conclusions which are of great importance in the investigation of the physical history of the earth. If the existing Classes, Orders, and Families of Marine and terrestrial Articulated animals have thus pervaded various geological epochs, since life began upon our planet, we may infer that the state of the Land and Waters, and also of the Atmosphere, during all these Epochs, was not so widely different from their actual condition as many geologists have supposed. We also learn that throughout all these epochs and stages of change, the correlative Functions of the successive Representatives of the Animal and vegetable kingdoms have ever been the same as at the present moment; and thus we connect the entire series of past and present forms of organized beings, as parts of one stupendously grand, and consistent, and harmonious Whole.
Proof of Design in the Structure of Fossil Radiated Animals, or Zoophytes.
The same difficulties which we have felt in selecting from other grand Divisions of the animal kingdom, subjects of comparison between the extinct and living forms of their respective Classes, Orders, and Families, embarrass our choice also from the last Division that remains for consideration. Volumes might be filled with descriptions of fossil species of those beautiful genera of Radiated Animals, whose living representatives crowd the waters of our present seas.
The result of all comparisons between the living and fossil species of these families would be, that the latter differ almost always in species, and often in genus, from those which actually exist; but that all are so similarly constructed on one and the same general Type, and show such perfect Unity of Design throughout the infinitely varied modications, under which they now perform, and ever have performed the functions allotted to them, that we can find no explanation of such otherwise mysterious Uniformity, than by referring it to the agency of one and the same Creative Intelligence.
The animals that compose this highest Class in the grand division of Radiated animals, viz. Echinidans, Stelleridans, and Crinoideans, have, till lately, been considered as made