Species of the Maera-clade collected from Japan. Part 2: genera Austromaera Lowry Springthorpe, 2005 and Quadrimaera Krapp-Schickel Ruffo, 2000 (Crustacea: Amphipoda: Maeridae).

One species of Austromaera Lowry Springthorpe, 2005 and four species of Quadrimaera Krapp-Schickel Ruffo, 2000 included in the Maera clade, are described from Japan. Austromaera ariakensis sp. nov. is described, based on collections from Ariake Sea and can be distinguished from its congeners by the acutely produced coxa 1 and the merus of gnathopod 2 with a small posterodistal spine. Quadrimaera gotoensis sp. nov. from Goto Islands in Nagasaki Prefecture has a small quadrate excavation on the middle palmar margin of the male gnathopod 2. This new species is different from Q. mirandella Appadoo, Myers Fagoonee, 2002 having such an excavation, in the larger posterodistal tooth of the male gnathopod 2 propodus and the wider bases of the pereopods 5-7. Quadrimaera pacifica (Schellenberg, 1938) was collected from many localities from Iwate Prefecture to Ariake Sea. This species is characterized by the transverse palm of the male gnathopod 2 with the large posterodistal tooth, the small rounded excavation in the middle and the anterior lobe narrower and produced more distally than the posterior lobe. Morphology of Q. pacifica is variable in the posterior excavation of the male gnathopod 2 palm, the uropod 3 rami and the distal end of the telson. Quadrimaera quadrimana (Dana, 1853) from the south of Yakushima Island in Kagoshima Prefecture has a distinct palm of the male gnathopod 2 with three excavations. Quadrimaera setibasis sp. nov. collected from the intertidal zone in Osaka Prefecture has a setose basis of the pereopod 6 like Q. schellenbergi (Ruffo 1938), but the bases of the pereopods 5 and 7 are not setose. A key to species of Austromaera in the world is provided.