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General Conclusions.

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.

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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 stu pendously grand, and consistent, and harmonious Whole.

CHAPTER XVII.

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.

SECTION I.

FOSSIL ENCHINODERMS.

THE animals that compose this highest Class in the grand division of Radiated animals, viz. Echinidans, Stelleridans, and Crinoïdeans, have, till lately, been considered as made

up of many similar parts disposed like Rays around a com

mon centre.

Mr. Agassiz has recently shown, (London and Edin. Phil. Mag. Nov. 1834, p. 369,) that they do not partake of this character, from which the division of radiated animals is named; but that their rays are dissimilar, and not always connected with a uniform centre; and that a bilateral symmetry, analogous to that of the more perfect classes of animals, exists throughout the families of Echini, Asteriam, and Crinoïdea.

ECHINIDANS AND STELLERIDANS.

The History of the fossil species of Echinidans and Stelleridans has been most beautifully illustrated, in the plates of the Petrefacten of Prof. Goldfuss. Though derived from Strata of various degrees of high antiquity, they are for the most part referred by him to existing Genera.

The family of Echinidans appears to have extended through all formations, from the Epoch of the Transition series to the present time.*

No fossil Stelleridans have yet been noticed in strata more ancient than the Muschelkalk.

As the structure of the fossil species of both these families is so nearly identical with that of existing Echini, and Starfishes, I shall confine my observations respecting fossil animals in the class of Echinoderms to a family which is of rare occurrence, excepting in a fossil state, and which seems to have prevailed most abundantly in the most ancient fossiliferous formations.

I found many years ago fossil Echinidans in the Carboniferous limestone of Ireland, near Donegal, they are however rare in the Transition formation, become more frequent in the Muschelkalk and Lias, and abound throughout the Oolitic and Cretaceous formations.

VOL. I.-27

CRINOIDEANS.

Among the fossil families of the Radiated division of animals, the Geologist discovers one whose living analogues are seldom seen, and whose vast numerical extent and extraordinary beauty entitle it to peculiar consideration.

Successions of strata, each many feet in thickness, and many miles in extent, are often half made up of the calcareous skeletons of Encrinites. The Entrochal Marble of Derbyshire, and the Black rock in the cliffs of Carboniferous limestone near Bristol, are well known examples of strata thus composed; and show how largely the bodies of Animals have occasionally contributed by their remains, to swell the Volume of materials that now compose the mineral world.

The fossil remains of this order have been long known by the name of Stone Lilies, or Encrinites, and have lately been classed under a separate order by the name of Crinoïdea.

This order comprehends many Genera and numerous Species, and is ranged by Cuvier after the Asteriæ, in the division of Zoophytes. Nearly all the species appear to have been attached to the bottom of the Sea, or to floating extraneous bodies.*

These animals form the subject of an elaborate and excellent work, by Mr. Miller, entitled a Natural History of the Crinoïdea, or Lily-shaped Animals. The representations at Pl. 48, and Pl. 49, Fig. 1. of one of the most characteristic species of this family, being that to which the name of stone-lily was first applied; and the figures of two other species at Pl. 47, Fig. 1, 2, 5, will exemply the following definition given of them by Mr. Miller. "An animal with a round, oval, or angular column, composed of numerous articulating joints, supporting at its summit, a series of plates, or joints, which form a cup-like body, containing the viscera, from whose upper rim proceed five articulated arms, dividing into tentaculated fingers, more or less numerous, surrounding the aperture of the mouth, (Pl. 47. Figs. 6, x. 7, x) situated in the centre of a plated integument, which extends over the abdominal cavity, and is capable of being contracted into a conical or proboscal shape."

The two most remarkable Genera of this family have been long known to Naturalists by the name of Encrinite and Pentacrinite; the former (see Pl. 49, Fig. 1, and Pl. 47, Figs. 1. 2. 5.) most nearly resembling the external form of a Lily, placed on a circular stem; the latter (see Pl. 51, and Pl. 52, Fig. 1, 3,) retaining the general analogies of structure presented by the Encrinite, but, from the pentagonal form of its stem, denominated Pentacrinite. A third Genus, called Apiocrinites, or Pear Encrinite, (Pl. 47. Figs. 1, 2.) exhibits, on a larger scale, the component parts of bodies of this family'; and has been placed by Mr. Miller at the head of his valuable work on the Crinoïdea, from which many of the following descriptions and illustrations will be collected.

Two existing species of recent animals throw much light on the nature of these fossil remains; viz. the Pentacrinus Caput Medusæ from the West Indies, represented at Pl. 52, Fig. 1. and the Comatula fimbriata,* figured in the first plate of Miller's Crinoïdea.

We will proceed to consider the mechanical provisions in the structure of two or three of the most important fossil species of this family, viewed in relation to their office as Zoophytes, destined to find their nourishment by spreading their nets and moving their bodies through a limited space, from a fixed position at the bottom of the sea; or by employing the same instruments, either when floating singly through the water, or attached, like the modern Pentelasmis anatifera, to floating pieces of wood.

Although the representatives of Crinoïdeans in our modern seas of rare occurrence, this family was of vast numeri

* The Comatula presents a conformity of structure with that of the Pentacrinite, almost perfect in every essential part, excepting that the column is either wanting, or at least reduced to a single plate. Peron states that the Comatula suspends itself by its side-arms from fuci, and Polyparies, and in this position watches for its prey, and attains it by its spreading arms and fingers. Miller, p. 182.

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