raphe

noun (plural raphae /ˈreɪfiː/)

• a groove, ridge, or seam in an organ or tissue, typically marking the line where two halves fused in the embryo, in particular:
• the connecting ridge between the two halves of the medulla oblongata or the tegmentum of the midbrain.
• Botany a longitudinal ridge on the side of certain ovules or seeds.
• Botany a longitudinal groove in the valve of many diatoms.