Adopting in a great measure the ar rangement of Waller, we shall commence our examination of the animal fossils with those which have derived their origin from corals. These fossils are, of course, merely the remains of the dwellings which have been formed by the various coral insects, and which are so frequently found in the cabinets of the curious.
Immediately on commencing this exa mination, we are struck with a similar want of agreement between the recent and fossil corals, with that which has been noticed between recent and fossil vegetables. Of the genus Tubipora it does not appear, at least by the obser vations made in Mr. Parkinson's second volume of " The Organic Remains of a former World," that a single species which is known recent has been found as a fossil. Several fossil species are, however, described, of which nothing similar is known in a recent state. The most striking of these is the Tubipora catenularia, or chain coral, the surface of which, in consequence of the tubes be ing in contact at their sides, has frequent ly a very curious reticulated or catenu lated appearance. Plate I. fig. 4, reprc sents this fossil in its usual state : and at fig. 5 is shewn the appearance yielded by a transverse section. Tubipora fascicu laris, T. stellata, T. repens, and T. strues, which have been described by different authors, and which are unlike to any known recent Tubipore, give reason for supposing that the number of species of fossil Tubipores exceeds that of the re cent species.
The fossil Mad repores are not less rich in variety, nor less comparatively nume rous, than the fossils of the preceding genus. The forms of several species of the fossil Madreporcs do frequently ap proach to those of the different recent species; but in a considerable number of the fossil Madrepores no resemblance is discoverable, except in their stelliform openings, with any recent coral. So great indeed is this departure in some instances from the general characters of our present known Madrepores, that it has been deemed difficult to determine, whether some fossil specimens should be considered as Madrepores or as Al cyonia. It is impossible, without the aid of numerous figures, to give satis flictory notions of the forms of the several fossil Madrepores which have been hitherto discovered ; the most in teresting only will therefore be here par ticularized.
The Madrepores consisting of a single star appear to be much more numerous in a mineral than in a recent state. These are either of a discoidal form, having a concave superior and a convex inferior surface ; of a pyramidal top-like form, terminating in a pedicle ; or of a length ened pyramidal form, bearing in some, from a slight curvature, the appearance of the horn of an animal ; whilst others are cylindrical for a considerable part of their length.
The first of these, Madrepora porpita, the shirt-button Madrepore, has been long known to the collectors of fossils in this kingdom. Dr. Woodward describes several of them, as mycetitz discoides. The second species (Madrepora turbina ta) is also frequently found in different parts of Great Britain, as well as in Swe den, Norway, and in several parts of France, Switzerland, and Italy. These latter fossils have been termed by Dr. Woodward mycetitx conoides seu calyci formes. When they have acquired some what of a hornlike shape, they have been distinguished by the term ceratites ; and when they have possessed more of the cylindrical form, they have been termed columelli lapidei et hippuritx ; and from a supposed resemblance, they have been also considered as the petrified roots of briony. Some of the single starred co rals are found united at their pellicle, and approaching towards each other at their summits, though disjoined nearly through their whole length. These, from their resemblance to petrified reeds, have been named junci lapidei.
It would be useless to attempt, in this sketch, to specify the considerable varie ty of fossil Madrepores formed of aggre gated circular stars, and which have been designated as astroites, &c. Those which are composed of angulated stars are, per haps, not so numerous : many of these, however, are very different in their ap pearance from those which are known in a recent state. The one most known in these islands is the lithostrotion, sive ba saltes striatus et stellatus, of Llwyd ; the exact union of the sides of the polygons giving a tolerably correct idea of minute basaltes. The compound Madrepores, the stelliform part of which are extend ed in undulating labyrinthean forms, appear to be much less numerous as fos sils than any of the other corals : their existence in a silieious state very rarely occurs.