Few genera of Fossil Fishes contain so large a number of welldefined species aa Agassiz' widely-distributed and well-known genus Pholidophorus. Above forty species have been more or less fully described by Agassiz and subsequent authors; the geological range extending from the Rhætic to the Purbeck Beds inclusive. The group consists mainly of small or moderate-sized fishes, but few that can be termed large; and with the exception of one species (P. maximus), the generic identity of which is doubtful, it contains no fishes of magnitude.