raphe

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Anatomy A seamlike line or ridge between two similar parts of a body organ, as in the scrotum.
• noun Botany The portion of the funiculus that is united to the ovule wall, commonly visible as a line or ridge on the seed coat.
• noun The median groove of a diatom valve.

from The Century Dictionary.

• noun In ornithology, the groove along the under side of the rachis of a feather.
• noun In botany: In an anatropous or amphitropous (hemitropous) ovule or seed, the adnate cord which connects the hilum with the chalaza, commonly appearing as a more or less salient ridge, sometimes completely embedded in a fleshy testa of the seed. See cuts under anatropous and hemitropous.
• noun A longitudinal line or rib on the valves of many diatoms, connecting the three nodules when present. (See nodule.) The usual primary classification of genera depends upon its presence or absence.
• noun In anatomy, a seam-like union of two lateral halves, usually in the mesial plane, and constituting either a median septum of connective tissue or a longitudinal ridge or furrow; specifically, in the brain, the median lamina of decussating fibers which extends in the tegmental region from the oblongata up to the third ventricle.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Anat.) A line, ridge, furrow, or band of fibers, especially in the median line.
• noun (Bot.) Same as Rhaphe.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun anatomy, botany A ridge or seam on an organ, bodily tissue, or other structure, especially at the join between two halves or sections.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a ridge that forms a seam between two parts