The prime purpose of this paper is to look at the region of brain which many authors call ‘paleocortex’ and to ask how much of the area it embraces can be described properly as cortex. Before this can be considered it is necessary to have some idea of what constitutes a cortex. Therefore, in the first part of the paper the criteria used in constructing classifications of cortex are looked into. Also considered is the meaning of classifications such as ‘paleocortex’. Is it relevant to define cortex in this way ? How does this view correlate with a functional approach ?