Mouthpart between the mandible and the 2nd maxilla. 1st maxilla possesses pseudexopod in Stylocheiron, Nematobrachion, and some Nematoscelis species. The true larval exopod presists only inPseudeuphausia sinica .

Alternative forms for first maxilla : 1st maxilla, 1st maxillae, first maxilla, first maxillae, maxillule.