Excerpt from A Monograph of the British Fossil Corals, Vol. 1: Introduction, Corals From the Tertiary and Cretaceous Formations 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 age 1 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 ...
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Excerpt from A Monograph of the British Fossil Corals, Vol. 1: Introduction, Corals From the Tertiary and Cretaceous Formations 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 age 1 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 Spongidae but the concentric lamellae of their stern contrasting with the fibrous structure of the tissue of the Sponge, will still render them recognisable. Dermal Corals are in general characterised by features 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 Spongidae. 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 operculum,2 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 Polypidom is equally reduced to a calcareous tube, tapering and closed at its base, Open and more or less enlarged at its upper end. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at ... This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.
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