Examples of delineations used to identify upper (UL) and lower layers (LL) in lemur (A, B), a cat (B, C), and a mouse (D, E). In some cases,, the boundary between upper and lower layers was distinguished by large cells located in the layer V. In cats, layer IV consists of stellate cells such that delineations were based on the presence of large cells in layer V as well as an increase in cell density in layer IV, when possible. In those cases, the presence of large cells in layer V was used to distinguish upper from lower layers. Scale bar: 1.5 mm.