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The Teleostei are modified Ganoidei. The Dipneusta gave rise to the Amphibia, which are the root of all other Vertebrata, inasmuch as out of them were developed the first Vertebrata provided with an amnion, or the Protamniota. The Protamniota split up into two stems, one that of the Mammalia, the other common to Reptilia and Aves.
Of the development of the Ganoidei we have unfortunately no knowledge, but their brains and their reproductive organs are more amphibian than are those of the Sharks.
But considering the close relation of the Mudfish with the Ganoidei, and the wide differences between the Elasmobranchii and the Teleostei, I greatly doubt the propriety of separating the Dipneusta, as a class, from the other Pisces.
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