zygocardiac

from The Century Dictionary.

• Noting a certain hard protuberance of the stomach of a crustacean, formed by a thickening of the chitinous lining of the cardiac division (in the crawfish an elongated posterolateral ossicle, connected with the lower end of the anterolateral ossicle, and passing upward and backward to become continuous with the pyloric ossicle): correlated with pterocardiac and urocardiac.