File:A guide to the fossil invertebrate animals in the Department of geology and palaeontology in the British museum (Natural history) (1907) (14776899354).jpg

Identifier: guidetofossilinv00brit (find matches)
Title: A guide to the fossil invertebrate animals in the Department of geology and palaeontology in the British museum (Natural history)
Year: 1907 (1900s)
Authors: British Museum (Natural History). Dept. of Geology Bather, Francis Arthur, 1863-
Subjects: Fossils
Publisher: London, Printed by order of the Trustees
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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-alleryVIII.Wall-case16. Wall-case18. Table-ease31. Table-case31. BetweenWall-cases16 & 17. Wall-case17. Class CYSTIDEA. The Cystids are of interest partly on account of their rarity, partly because they are all extinct, none having survived the Carboniferous Epoch, partly by reason of their diversity and strangeness of structure, but mainly becausethey are thought to comprise forms from which other classes 64 GUIDE TO THE FOSSIL INVEETEBEATE ANIMALS. Gallery of Echinoclerma have descended and to approach most nearlythose pre-existing animals from which the Echinoderma were Table-ease originally derived. The best British specimens are from theW ll^c se ^^^^-^^^^ Limestone; but other horizons are well represented\q^^^^ by those from Bohemia, Eussia, ISTorth America and other foreign countries. Among the older and more primitive are many, such as Aristocystis (Fig. 29 a), that appear to have been little more than plated sacks, without stem or arms : U7VUS go-noJooTeUHxIer-pore ~ ~rrvoxdh -
Text Appearing After Image:
Fig. 29.—Types of Cystidea. a, Sack form with scattered pores, Aristo-cystis. b, Example of Rhombifera, with food-groove skeleton slightly developed, Echinosphaera. c, Example of Diploporita, Protocrinus;the brachioles are restored on the right side; elsewhere are seen the facets that supported them, d, Example of Rhombifera, with food-groove skeleton highly developed, and with respiratory folds restricted to three pectini-rhombs, of which one is shown near the top of the right-hand quarter; Lepadocrinus, hence the name of the class, which means sack-shaped.These, however, probably all had ciliated food-grooves stretch-ing from the mouth, either along fleshy tentacles or along similar processes provided with a calcified support or skeleton.These processes are called brachioles, and there is no reason to suppose that they contained such extensions of the body-cavity, of the reproductive organs, or even of the hydraulic system, as occur in Crinoidea. Hence we suppose that a ECHINODEEMA—CYS

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