Hyalella cajasi sp. n., male. A head with left antenna 1 and antenna 2 attached, lateral B inset of distomedial armature on posterior margin of articles 3-6 of antenna 1 C right epimeral plates D right pleopod 3, posterior. Scale bars: 0.2 mm (A, D); 0.1 mm (B); 0.5 mm (C, E, G–I); 0.05 mm (F).