Claus, 1879
Length 3-4 mm (Amphithyrus bispinosus 1). CX V strongly pointed, projecting laterally (Amphithyrus bispinosus 4, unique character for this genus!). Posterodistal process of ART 5 of P II reaching top of sub-distal denticle of ART 6 (Amphithyrus bispinosus 3). ART 2 of P V two thirds as long as distal ART combined. P VII consisting of narrow ART 2 with rounded top, sometimes 1-2 rudimentary distal ART (Amphithyrus bispinosus 5). Telson triangular, with pointed top, slightly longer than fused (II+III) urosomite.