Fig. 2 in The morphology and fine structure of the Ordovician Cephalodiscus-like genus Melanostrophus

Fig. 2. Melanostrophus fokini Öpik, 1930; Upper Ordovician (Kukruse Stage, C β), Ubja (Estonia); ZPAL Pb 6/1. SEM micrographs of chemically 2 isolated fragments. A. Fragment of a single tube with a fragment of apertural margin. B, C. Broken bundles of tubes. Abbreviations: a, apertural margin; f, interfusellar suture; i, interior of the tube; p, periderm perforations; t1, t2, etc., adjacent tubes. Arrows show circular cross section of the tubes.