[A. Retzius (1796–1860), Swedish anatomist] Incremental growth lines found in developing enamel, which indicate weekly variation in mineralization. They microscopically appear as a series of dark bands. Formed as a result of the constriction of the Tomes processes, they run obliquely from the amelodentinal junction to the enamel surface, where they produce a series of grooves (perikymata). The first 30–40 striae are obscured under the incisal edge. The average human incisor contains about 150 brown striae and the spacing between the striae represents about 7 days' growth; they have therefore been used for determining the age of death in contemporary humans and fossil hominids.