During the last few years the importance of the flake cultures of the lower Palaeolithic has been recognised by prehistorians, and great advances have been made towards the correlation of these industries with the various biface cultures, and in the working out of their stratigraphical sequence. The position of the Clactonian has been firmly established, and the long neglected Levalloisian industry is now assuming its proper place of importance. Much confusion has been caused in the past by the misleading nomenclature of these two industries. The Clactonian was often called Abbevillian (Chellian), or Acheulian, and the evolved Clactonian, Mousterian. The Levalloisian was believed to be a part of the Acheulian, and was also frequently miscalled Mousterian. These two flake cultures, sometimes dovetailing with, and sometimes running parallel to the biface industries, culminate in the Mousterian, when they join, via the Tayacian, with the Acheulian biface technique to form a polymorphic culture; the local variations of this usually combine at least two of the techniques. These variations are in a great respect governed by the quality and size of the blocks of material available for making artifacts.