For some years it has appeared to me that in the Order Theriodontia as generally accepted there were included a number of forms not at all nearly related to the typical genus, Galesaurus, and in a number of papers I have referred to these as ‘Primitive Theriodonts.’ The best known genera are Ælurosaurus and Ictidosuchus, but as in neither of these have the details of palatal structure been very clearly made out, it has been impossible to say how far they differed from the typical Theriodonts.