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I can note only a few points which seem to me to be open to discussion. The Monorhina, having been developed out of the Leptocardia, gave rise, according to Professor Haeckel, to a shark-like form, which was the common stock of all the Amphirhina. From this "Protamphirhine" were developed, in divergent lines, the true Sharks, Rays, and Chimaerae; the Ganoids, and the Dipneusta.
The only modification which it occurs to me to suggest in this general view of the Phylogeny of the Vertebrata is, that the "Protamphirhine" was possibly more ganoid than shark-like.
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