Unlike other gyrinid species, the chorionic surface ofDineutes horniis covered with blunt conical projections. The micropylar region consists of a stalk‐like structure in the center of a depression. Internally the chorion consists of an exo‐ and endo‐chorion. The outer chorion has large spaces and is composed of a laminated and porous material, whereas the inner chorion is made‐up of a thick granulated layer and a thin electron‐dense layer. The vitelline membrane has an electron‐dense upper surface and spherical, vesicular‐like structures that are dispersed throughout the membrane.