|Anatomical terms of neuroanatomy|
The allocortex or heterogenetic cortex, and neocortex are the two types of cerebral cortex in the brain. The allocortex is the much smaller area of cortex taking up just ten per cent; the neocortex takes up the remaining 90 per cent.  It is characterized by having just three or four cortical layers, in contrast with the six layers of the neocortex. There are three subtypes of allocortex: the paleocortex, the archicortex, and the periallocortex – a transitional zone between the neocortex and the allocortex. 
Allocortex is termed heterogenetic cortex, because during development it never has the six-layered architecture of homogenetic neocortex. It differs from heterotypic cortex, a type of cerebral cortex, which during prenatal development, passes through a six-layered stage to have fewer layers, such as in Brodmann area 4 that lacks granule cells. 
The allocortex has three or four layers of neuronal cell bodies, in contrast to the six layers of the neocortex. There are three subtypes of allocortex: the paleocortex, archicortex and periallocortex. 
Paleocortex is a type of thin, primitive cortical tissue that consists of three cortical laminae (layers of neuronal cell bodies).   The two granular layers II and IV of neocortex are absent in paleocortex. The main areas of paleocortex are the olfactory bulb, olfactory tubercle and piriform cortex.
Periallocortex is a transitional form between neocortex and either paleo- or archi-cortex. It thus can be either peripaleocortex (anterior insular cortex) or periarchicortex ( entorhinal cortex, presubicular cortex, retrosplenial, supracallosal, and subgenual areas).
Because the number of laminae that compose a type of cortical tissue seems to be directly proportional[ citation needed] to both the information-processing capabilities of that tissue and its phylogenetic age, and also because olfaction is a major sensory modality in phylogenetically early animals, paleocortex is thought to be the most primitive form of cortex. 
- Saladin, K (2012). Anatomy & physiology : the unity of form and function (6th ed.). New York, NY: McGraw-Hill. p. 417. ISBN 9780073378251.
- Crosby EC; Humphrey T; Lauer EW (1962)Correlative Anatomy of the Nervous System. New York: MacMillan
- Filimonoff, IN (1947). "A rational subdivision of the cerebral cortex". Arch Neurol Psychiatry. 58 (3): 296–311. doi: 10.1001/archneurpsyc.1947.02300320047002. PMID 20265596.
- "Paleocortex". BrainInfo. University of Washington. Retrieved 5 May 2013.
- Purves, Dale; Augustine, George J; Fitzpatrick, David; Hall, William C; LaMantia, Anthony-Samuel; White, Leonard E (2011). Neuroscience (5th ed.). Sinauer Associates Inc. p. 666. ISBN 9780878936465.
- "Archicortex". BrainInfo. University of Washington. Retrieved 17 March 2017.