[Copepoda] Abbr. for
— fourth internal lobe or basal endite of maxillule (Mx1).
— fourth lobe or coxal endite of maxilla (Mx2).
— syncoxal endite of the maxilliped (Mxp).

(Fig. Co.1f , Mx1 maxillule)
(Fig. Co.1g , Mx2 maxilla)
(Fig. Co.1e , Mxp maxilliped)