[Copepoda] Abbr. for
— first internal lobe or praecoxal arthrite of the maxillule (Mx1).
— first lobe or praecoxal endite of the maxilla (Mx2).
— praecoxal endite of the maxilliped (Mxp).

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