Zygobranchia

from The Collaborative International Dictionary of English v.0.48
Zygobranchia \Zyg`o*bran"chi*a\, n. pl. [NL., from Gr. zygo`n a
   yoke + ? 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]
    

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