That the Upper Cretaceous deposits overlap those of the Lower Cretaceous series, and extend over much larger areas throughout the whole of western and central Europe, are facts which have long been familiar to all European geologists. There has, however, been a tendency, especially in France, to imagine that the subsidence to which the overlap is due took place at one particular epoch, namely, the Cenomanian, and that this subsidence was so rapid and profound that it caused the Upper Cretaceous Series to be sharply marked off from the subjacent strata by the so-called ‘Cenomanian transgression.’