The ethmoidal infundibulum is a funnel-shaped/slit-like/curved opening/passage/space/cleft upon the anterosuperior portion of the middle nasal meatus (and thus of the lateral wall of the nasal cavity) at the hiatus semilunaris (which represents the medial extremity of the infundibulum).
A funnel-shaped passage in the nasal cavity, situated on the front superior portion of the middle nasal channel, is defined by the hiatus semilunaris, which represents its medial extremity.