Wiktionary
n. (context anatomy English) The dorsal posterior segment of the diencephalon; it includes the habenula, the stria medullaris and the pineal body.
Wikipedia
The epithalamus is a (dorsal) posterior segment of the diencephalon. The diencephalon is a part of the forebrain that also contains the thalamus, the hypothalamus and pituitary gland. The epithalamus includes the habenula and their interconnecting fibers the habenular commissure, the stria medullaris and the pineal gland.
Usage examples of "epithalamus".
Yes, there was the telencephalon and there the diencephalon, with the thalamus and epithalamus and metathalamus.
He not only breathed deeply from the pleasure of it, like a termite in the heavy, damp, conditioned air of its nest, but was also drunk on this gas, which not only nourished his lungs and stomach, but also, with its smell, his epithalamus, nerves and sexual apparatus.