What is "caesiosoma californiense"

Half-moon \Half"-moon`\ (-m[=oo]n`), n.

1. The moon at the quarters, when half its disk appears illuminated.

2. The shape of a half-moon; a crescent.

   See how in warlike muster they appear, In rhombs, and wedges, and half-moons, and wings.
   --Milton.

3. (Fort.) An outwork composed of two faces, forming a salient angle whose gorge resembles a half-moon; -- now called a ravelin.

4. (Zo["o]l.) A marine, sparoid, food fish of California ( C[ae]siosoma Californiense). The body is ovate, blackish above, blue or gray below. Called also medialuna.