heteropod a

pl. [Pref. hetero-, and Gr. pod a, pl. pous (gen it. podos ) = a foot.] 1. Zool .: A group of branchial gasteropod a, in which the pro podium is turned into a laterally compre ed fin, while the epipodia are absent-i. e., in which the foot is so modified as to form a swim ming organ. ( Hurley, .) The Heteropod a are same as Nucleobranchiata (q. v.) of De Blain ville, and S. O. Woodward prefers the latter name. They are delicate and transparent animals, some only with shells. They swim at the surface of the sea instead of creeping at the bottom. Families Firolide and Atlantide. 2. Palæont .: The Heteropod a came into being not later than the Lower Silurian.