A guide to the fossil invertebrate animals in the Department of geology and palaeontology in the British museum (Natural history) . enestrae only, c, section of same, passing from near obverse surfaceon left to near reverse surface on right, a and b magnified 9 diameters;c, 18 diameters. (After E. 0. Ulrich.) Stomatopora, Berenicea (Fig. 64). In the Cheilostomata^which reached their present dominant position in Cainozoictime, the opening is removed from the end of the chamber,is constricted, and provided with a movable lid (operculum). BEYOZOA OE POLYZOA. 119 Examples : Flusira (Fig. 61), Memh
A guide to the fossil invertebrate animals in the Department of geology and palaeontology in the British museum (Natural history) . enestrae only, c, section of same, passing from near obverse surfaceon left to near reverse surface on right, a and b magnified 9 diameters;c, 18 diameters. (After E. 0. Ulrich.) Stomatopora, Berenicea (Fig. 64). In the Cheilostomata^which reached their present dominant position in Cainozoictime, the opening is removed from the end of the chamber,is constricted, and provided with a movable lid (operculum). BEYOZOA OE POLYZOA. 119 Examples : Flusira (Fig. 61), Memhranipora (Fig. 65 a), Ony- Galleryclwcella (Fig. 65 I). VIII. In many Bryozoa certain individuals are modified forspecial duties. Tiius in the Cheilostomes the growth of theoperculum has produced snapping beaks, called avicularia,and long movable bristles, called vibracula; the positionsoccupied by these appendages can be detected in the fossils(Fig. 65). Sometimes individuals are set apart and modifiedfor reproduction, sometimes special pouches for the receptionof the developing eggs are attached to the chambers (Fig. 65 a).. Fig. 64.—Cyclostomatous Bryozoa from the Bathonian (Bradford Clay) ofEngland, a, Stomatopora dicJwtoma, part of an encrusting colony,natural size, and magnified 25 diameters, b, Be7enicea compressa, anencrusting colony, natural size, and part of it 12 diameters.(After J. W. Gregory.) These modifications suggest explanations for the smallerchambers and tubes interspersed among the normal ones inthe fossils of extinct Orders. We may now briefly review the exhibited British series begins with some from the Ordovician Case A5,rocks of Wales. These are so poorly preserved that they ^^^^can only be determined by the help of better specimens fromAmerican rocks of the same age. Most of them are Trepo-stomes or Cryptostomes. The Silurian Bryozoa are in a better state, and the Case A5,specimens from the Wenlock Limestone include some ^©^
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