Keywords: Origin of Vertebrates Fig 074.jpg Fig 74 ”Ventral half of Head-region of AmmocĹ“tes Somatic muscles coloured red Branchial and visceral muscles coloured blue Tubular constrictor muscles distinguished from striated constrictor muscles by simple hatching Tent tentacles; Tent m c muco-cartilage of tentacles; Vel m c muco-cartilage of the velum; Hy m c muco-cartilage of the hyoid segment; Ps br pseudo-branchial groove; Br cart branchial cartilages; Sp space between somatic and splanchnic muscles; Th op orifice of thyroid; H heart All references in this work to AmmocĹ“tes or Petromyzon appear to refer to the species now called Lampetra planeri 1908 The Origin of Vertebrates https //archive org/details/ost-biology-the_origin_of_vertebrates Walter Holbrook Gaskell PD-old-auto-1923 1914 Origin of Vertebrates book Lampetra planeri |