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The material for this work was that collected and prepared by Professor J. Graham Kerr in the Chaco (Lepidosiren), and by Budgett from the Gambia (Protopterus). The process of development follows nearly the same course in the two genera, and where differences occur they are mainly such as are to be expected from a comparison of the adult skulls. While the series of stages ofLepidosirenleft no unfilled gaps, the material was scantier in the case ofProtopterus. Except where otherwise stated, thedoi:10.1017/s0080456800011637 fatcat:nujejlymyjdlhplh4544raolqq