Author: J. W. Gregory

Publisher: Forgotten Books

Published: 2018-01-31

Total Pages: 304

ISBN-13: 9780267392346

Excerpt from Catalogue of the Fossil Bryozoa: In the Department of Geology British Museum (Natural History), The Jurassic Bryozoa To the zoologist, who can base his classification upon the soft parts of the animal, as well as upon the hard, these tubicolar forms present no exceptional difficulties. They are, indeed, of especial interest, for they show how close a resemblance may exist between animals of different groups, owing to adaptation to suit the same conditions of life; and they supply the most emphatic warning that similarity in structure does not always imply community of origin. To the palaeontologist, however, who cannot check his con elusions by the evidence of vascular anatomy or embryology, these tube-dwelling animals are a vexation and a puzzle. There is so frequently no correlation between the structure of the tube and of the creature that made it. Hence the vast majority of the fossil worm tubes are now ignored by palaeontologists; their study has been abandoned in despair, for, so far as we can see at present, they can give no aid in the classification of the group to which they belong, or in tracing its life history. In the study of the Jurassic Bryozoa we are faced by the initial difficulty that their shells are tubular. In periods earlier than the Jurassic, many of the Bryozoa belonged to the order Cryptostomata; and in later times the order Cheilostomata was well represented. In these two groups the skeletons of the individual members of the colony are complex, and offer fairly reliable diagnostic characters. But in Jurassic times the former order was extinct, and the latter was represented by only two rare species; per cent. Of the forms have left no traces, except their tubular skeletons. Nevertheless, these fossils cannot be ignored like the worms, for, with the two exceptions noted, they belong to orders either wholly extinct or now of dwindling importance. Their evidence, therefore, must be considered in any attempt to trace the evolution of the Bryozoa. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com 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.