The right hemisphere (upper and lower left, and left half of basal view) shows an unusually large area of supply of the ACA, extending beyond the parieto-occipital fissure to the cuneus. The posterior internal frontal artery is absent. The callosomarginal artery gives rise to the anterior and middle posterior frontal and the paracentral arteries (yellow area). The black line subdivides the cross-hatched area of the paracentral artery to show the two separate branches arising from the pericallosal artery to supply the area of the paracentral artery. The left hemisphere (upper and lower right, and right half of basal view) shows an unusually small area of supply of the ACA. The branches reach only the paracentral area. The callosomarginal artery gives origin to two cortical branches: the middle and posterior internal frontal arteries (yellow area). The superior and inferior parietal arteries are absent. The black line divides the orbitofrontal area (blue lines) to show that it was supplied by two separate branches of the pericallosal artery. (Images coutesy of AL Rhoton, Jr.)