The term area OB of Bonin refers to an area of the occipital lobe in the macaque defined on the basis of cytoarchitecture. It is located immediately anterior to area OC of Bonin. The boundary with area OC is defined distinctly by the abrupt thinning of the prominent internal granular layer of OC. Near the margin "there are especially large cells in iiic to form what Economo calls in man OB gamma," a finding reported in many primate species. The anterior boundary of area OB with area OA of Bonin is very indistinct ( Bonin-1947 ).