Keywords: Origin of Vertebrates Fig 160.png Fig 160 ”A Diagram of Section through a Trilobite-like Animal; B Diagram to illustrate Suggested Obliteration of Appendages and the Formation of an Atrial Cavity by the Ventral Extension of the Pleural Folds; C Diagram to illustrate the Completion of the Vertebrate Type by the Meeting of the Pleural Folds in the Mid-ventral Line and the Obliteration of the Atrial Cavity Al alimentary canal; N nervous system; My myotome; Pl pleuron; App appendage; Neph nephrocĹ“le; Met metacĹ“le; S d segmental duct; At atrial chamber; V Mes ventral mesentery; Mes mesonephros The dotted line represents the splanchnopleuric mesoblast in all figures 1908 The Origin of Vertebrates https //archive org/details/originofvertebra1908gask Walter Holbrook Gaskell PD-old-auto-1923 1914 Origin of Vertebrates book Trilobita fossils |