"To the distinctive set of characters given by Müller we may probably add the following:
"(1) Oviducts and urinary ducts always unite, and open by a common urogenital aperture behind the anus.
"(2) Skull hyostylic.
"(3) Segmentation complete in the types so far investigated, though perhaps Amia may be found to resemble the Teleostei in this particular.
"(4) A pronephros of the Teleostean type present in the larva.
"(5) Thalamencephalon very large and well developed.
"(6) The ventricle in the posterior part of the cerebrum is not divided behind into lateral halves, the roof of the undivided part being extremely thin.
"(7) Abdominal pores always present.
"The great number of characters just given are amply sufficient to differentiate the Ganoids as a group; but, curiously enough, the only characters, amongst the whole series which have been given, which can be regarded as peculiar to the Ganoids are (1) the characters of the brain, and (2) the fact of the oviducts and kidney-ducts uniting together and opening by a common pore to the exterior.
"This absence of characters peculiar to the Ganoids is an indication of how widely separated in organization are the different members of this great group.