A monograph of the British fossil corals - kreidefossilien.de

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ii BRITISH FOSSIL CORALS. monly thus blended together. For us the word Coral, or Corallum, must be synonymous with Polypidom,^ and signify the hard or ossified parts of the body of a Polyp. In treating of the " Fossil Corals of Great Britain," we must, therefore, exclude from our investigation the various organic remains which bear a certain resemblance to Polypidoms, but which do not in reality belong to beings of the same structm-e, and we must cu'cumscribe om- researches within the boundaries of the group of Zoophytes, which, in a Natm'al arrangement of the Animal Kingdom, is represented by the Class of Polypi.^ These Zoophytes are closely allied to Medusae, and in the actual state of science there is some uncertainty respecting the natural Umits which separate these two groups ; but the mode of organization common to both is so characteristic, that the most superficial anatomical investigation wiU always enable the zoologist to distinguish a Polyp or an Acaleph from the Bryozoa and the Spongida3, which, till lately, have been erroneously considered as belonging to the class of Corals. Polypi have a radiate structm'e ; a protractile mouth, smTounded by non-ciliate tentacula ; a large and well-organized digestive cavity ; but have no anus. In Spongidse no appearance of tentacula or of a stomach is ever met with ; and in Bryozoa an intestinal canal, much resembling that of ordinary MoUusca, is always provided with two distinct openings, a mouth and an anus, the first of which is encu-cled by ciliated tentacula. The structm-e of the digestive organs is, therefore, characteristic in all these animals, and in most instances the radiate form of the tegumentary system vdll alone suffice to render the diagnosis of Polypi an easy task. But when the Polypidom is reduced to its most simple condition, it sometimes bears great resemblance to the calcareous or horny covering of certain Bryozoa, or to the reticulate skeleton of some of the Spongidse ; and the Polypidom being the only part of these animals which is found in the fossil state, it is sometimes hard for the palaeontologist to decide whether the organic remains that assume this form are in reality Corals, or whether they do not belong to one of the other above-mentioned Zoological divisions. Polypidoms may present two very distinct forms. Some, belonging to aggregate Polypi, are developed on the basal surface of these Zoophytes, and constitute a sort of stem in the ' In translating the French expression Polypier by the word Polypidom, which has of late been adopted by some of the most eminent English zoopliytologists, we deem it necessary to guard the reader against the erroneous ideas which the etymology of that name might lead to. Till of late the nature of Corals was in general misunderstood ; they were supposed to be produced by a plastic exudation moulded round the body of the Polyp, and serving as a dweUing for these singular beings, but not forming a part of their organism. Such is far from being the case ; the corallum is a part of the animal, in the same way as the coating of the armadillo or the shell of the lobster belong to the structure of these beings. The words " Polypidom," Polypier, &c., might therefore be objected to, if their meaning was not generally known, and had not become independent of their etymology. - The class of Polypi, reduced to its natural limits, corresponds to the Anthozoa of M. Ehrenberg, and to the sub-class of Radiated Zoophytes of Mr. Johnston. In the excellent work recently published by Mr. Dana, the same group is designated by the name of Zoophytes, which is usually employed in a much wider acceptation, and had long ago been given by Cuvier to the great division of radiate animals, comprising Echinoderma and Acalephse, as well as Polypi, etc.
INTRODUCTION. iii centre of the ramified mass produced by the multipUcation of these plaiit-hke animals. denth'oid red Coral of the Mediterranean Sea and the horny skeleton of Gorgonia are thus inclosed in the axis of cylindrical branches, formed by the thick coriaceous tegumentary tissue belonging to the whole community of aggregate Polypi, and studded, as it were, by the radiate protractile heads of the many individual Zoophytes thus united. Other Corals, appertaining either to simple or to compound Polypi, are, on the contrary, produced by the ossification of this tegumentary tissue itself, and instead of forming a sort of stem, constitute a sheath, or an assemblage of calcareous tubes, each of which belong to an individual Zoophyte, correspond to the lower part of its digestive cavity, and serve as a kind of cell or lodge into which the anterior portion of the animal's body recedes when in a contracted state. The basal or stalk-like Corals are in general well characterised by their dendroid form, compact tissue, and concentric layers. At first sight they may bear a slight resemblance to certain Bryozoa that have attained a very advanced ageji but even then the remains of some non-obliterated cells will always enable an attentive observer to recognise the latter, and the absence of all trace of any such cavities can easily be ascertained, by grinding down or fracturing the stem of the above-mentioned Zoophytes. In some few instances these basal Polypidoms are more like the reticulated skeleton of certain foliaceous Spongidaj ; but the concentric lamellae of their stem contrasting with the fibrous structure of the tissue of The the Sponge, will still render them recognisable. Dermal Corals are in general characterised by featm-es of a more striking aspect, and it is only when these Polypidoms are reduced to their most simple and degraded form, that they can be mistaken for the tegumentary skeleton of some of the lowest Bryozoa, or the reticulate, stony tissue of some highly-organized Spongidaj. In all well-developed Corals of this kind, the central cavity or visceral chamber is more or less completely divided by a certain number of vertical plates, which project from its walls towards its axis, and produce that radiate structure which is so remarkable in the Astrean tribe. In most Bryozoa the mouth, or cephalic aperture of the tegumentary cell, is provided with a horny opercuhmi," but no such organ ever exists in a true Coral ; and, on the other hand, the radiate septa which we have just alluded to as being conspicuous in most Polypidoms, never exist in the cells of Bryozoa. The absence of an operculum, or of vertical septa, will not, however, enable the observer to decide whether the coral-like organic remains submitted to his investigation belong to the one or to the other of the two great zoological divisions, for it is a well-known fact that, in many of the inferior forms among recent Bryozoa, the tegumentary skeleton is reduced to a simple non-operculated tubular sheath, and that in certain Polypi (the Tubipora for example), no longitudinal septa are to be found ; and the Polyjjidom is equally reduced to a calcareous tube, tapering and closed at its base, open and more or less enlarged at its upper end. ^ Tlie Millepora truncata of Ellis and Solander, for example. - See "Recherches sur les Esehares," Annales des Sciences Naturelles, 2"' serie, t. vi, pi. i.
Page 5: THE PALiEONTOGRAPHICAL SOCIETY. INS
Page 8 and 9: i. E. ADLJIED, PBINTr.B, BARTHOLOME
Page 10: e 7b-^,pi'? PRINTED BY C. AND .1. A
Page 15 and 16: INTRODUCTION. v certain parts of th
Page 17 and 18: INTRODUCTION. vii in which the mult
Page 19 and 20: INTRODUCTION. ix Sub-class 1. CORAL
Page 21 and 22: ; INTRODUCTION. xi Sub-order 1. ZOA
Page 23 and 24: INTRODUCTION. xiii 3. Genus Acantho
Page 25 and 26: ; INTRODUCTION. xv formed by proces
Page 27 and 28: ; INTRODUCTION. xvii IS. Genus Plat
Page 29 and 30: INTRODUCTION. xix Aberrant Group. P
Page 31 and 32: INTRODUCTION. xxi 8. Genus Amphelia
Page 33 and 34: INTRODUCTION. xxiii 3. Genus Dkndra
Page 35 and 36: INTRODUCTION. xxv 5. Genus Ccelosmi
Page 37 and 38: INTRODUCTION. xxvii in the two prec
Page 39 and 40: ; INTRODUCTION. xxix 23. Genus Pler
Page 41 and 42: ; INTRODUCTION. xxxi 30. Genus Hete
Page 43 and 44: INTRODUCTION. xxxiii 30. Genm Symph
Page 45 and 46: ;; INTRODUCTION. xxxv 44. Gentts Tr
Page 47 and 48: LNTRODUCTION. xxxvii 50. Genus Dipl
Page 49 and 50: INTRODUCTION. xxxix Section IV.—
Page 51 and 52: ; INTRODUCTION. xli 64. Genus Astro
Page 53 and 54: INTRODUCTION. xliii which thus form
Page 55 and 56: ; INTRODUCTION. xlv 79. Genus Oclan
Page 57 and 58: INTRODUCTION. xlvii 4. Genus Micbab
Page 59 and 60: INTRODUCTION. xlix 14. Genus Ctclos
Page 61 and 62:
INTRODUCTION. li the sclerenchyma,
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INTRODUCTION. liii 7. Genus Stephan
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INTRODUCTION. Iv Family VII. PORITI
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. INTRODUCTION. Ivii Second Tribe
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INTRODUCTION. lix 4. Genus Fistulip
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INTRODUCTION. hi but much shorter,
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INTRODUCTION. Ixiii Family X. SERIA
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; INTRODUCTION. Ixv Family XIII. CY
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INTRODUCTION. kvii 7. Gejius Hallia
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INTRODUCTION. hix 17. Genus Gonioph
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INTRODUCTION. Ixxi or costal radii
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INTRODUCTION. • Ixxiii The genera
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INTRODUCTION. Ixxv Family I. ALCYON
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INTRODUCTION. Ixxvii Second Tribe
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INTRODUCTION. Ixxix 1 7. Ge?ius Dis
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INTRODUCTION. Ixxxi 8. Genus Soland
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INTRODUCTION. Ixxxiii 3. Ge7lUS ViR
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INTRODUCTION. Ixxxv Order 3. PODACT
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CORALS OF THE UPPER CHALK. 46 towar
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CORALS OF THE UPPER CHALK. 47 Famil
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: CORALS FROIM THE UPPER CHALK. 49
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CORALS FROM THE UPPER CHALK. 51 Tho
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CORALS FROM THE LOWER CHALK. 53 CHA
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CORALS FROM THE LOWER CHALK. 55 the
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CORALS FROM THE UPPER GREENSAND. 57
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; CORALS FROM THE UPPER GREENSAND.
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CORALS FROM THE GAULT. CHAPTER VI.
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; CORALS FROM THE GAULT. 03 3. Genu
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CORALS FROM THE GAULT. 65 found nea
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CX)RALS FROM THE GAULT. G7 and have
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' Petref. : ; CORALS FROM THE GAULT
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; CORALS FROM THE LOWER GREENSAND.
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TAB. IX. CORALS FROM THE UPPER CHAL
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TAB. XI. CORALS FROM THE GAULT. Cya
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302 TABLE OF BRITISH FOSSIL CORALS.
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304 TABLE OF BRITISH FOSSIL CORALS.
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A. GENERAL INDEX;
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308 GENERAL INDEX.
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310 GENERAL INDEX.
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312 GENERAL INDEX. Dendrophyllia de
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314 GENERAL INDEX. . Halysites cate
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310 GENERAL INDEX.
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318 GENERAL INDEX.
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320 GENERAL INDEX.
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322 GENERAL INDEX. Xenia Zaphrentis
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