A Glance at the exhibited collections in any of our leading museums, such as the British Museum, the Geological Survey Museum, or the Oxford University Museum, shows that the naming and identification of many of the Mesozoic fossils is in a very unsatisfactory state. The private collector or the student who becomes thoroughly familiar with the fauna of his own district and then goes to these museums to classify and identify it will usually come away with many misconceptions. He finds, moreover, that the various museums contradict one another.