Giesbrecht, 1892
Female Pr wide and Ur narrow. Pr of 5 somites, Ur of 5-6 somites; Ur1 and 2 either separated only on dorsal surface or completely around. Ce prolonged into point. CR short, fused to last Ur somite and fused in median line; carrying 2 large setae. A1 6-7-segmented with long sensory organs and segment 3. Md reduced to 1 toothed blade. Mx1 without Enp. Mx2 elongate; Li5 with 1 thickened pickaxe-like seta. Mxp small, 2-segmented. Mx2 and Mxp rudimentary in male. Basis of P wide; P1-4 rami 3-segmented. P5 rudimentary, elongate, 1-segmented. P6 relatively large, 1-segmented (from Rose, 1933; Wells, 1970).
Both species, Aegisthus aculeatus and Aegisthus mucronatus, of the only genus Aegisthus Giesbrecht, 1891 in the family, are known from the South Atlantic.