calotte

noun

1. A skullcap worn by Roman Catholic priests.
2. (archaic)The vertical central area of the crown of a bird's head.
3. A round cavity or depression, in the form of a cup or cap, lathed and plastered; used to diminish the rise or elevation of a moderate chapel, alcove, etc. which would otherwise be too high for other pieces of the apartment.
4. The upper (superior) or lower (inferior) half of the globe of the eye.