FIGURE 2 in Deep-sea serpulids (Annelida: Polychaeta) in tetragonal tubes: on a tube convergence path from the Mesozoic to Recent

FIGURE 2. Tube ultrastructures of Bathyditrupa hovei. A–D: PIN 5485/08, A—longitudinal wall section, B—enlarged outer wall part, C—enlarged middle wall part consisting of elongated crystals, D—enlarged inner wall part showing a thin layer of smaller isometric crystals. E: PIN 5485/09, middle wall part showing loose transverse orientation of crystals (oblique section). F: PIN 5485/11, longitudinal wall section. G–I: PIN 5485/15, a series of tube fragments of different sizes (may belong to different specimens) showing no principal ultrastructural ontogenetic changes. Arrows indicate direction of tube growth. Abbreviation: o. s.—outer tube surface.