Fornix (pl. fornices): One of a set of small crests or scales in the throat of a corolla, as in many of the Boraginaceae.*
This Brunnera has pale yellow fornices which form the ‘eye’ at the centre of each flower. Myosotis (forget-me-nots), which are also members of the Boraginaceae family, usually have bright yellow fornices.
*Harris, J.G., Harris, M.W. (2001). Plant identification terminology: An illustrated glossary (2nd ed.). Spring Lake: Spring Lake Publishing.