zygobranchia

‖n. pl. [ NL., from Gr. zygo`n a yoke + &unr_; a gill. ] (Zool.) A division of marine gastropods in which the gills are developed on both sides of the body and the renal organs are also paired. The abalone (Haliotis) and the keyhole limpet (Fissurella) are examples. [ 1913 Webster ]