The structure of the ctenidium of the top shell, Turbo cornutus, was examined with corrosion casts and histological structures. The casts were made using the prepolymerization methyl methacrylate (MercoxCL-2 R) containing 10 % Mercox MA. The ctenidial plate was constructed with two triangular walls connected to each other by many trabeculae. The interior space of each ctenidial plate was communicated with the blood vessel of ctenidial axis (CAV) which joined the afferent branchial vessel (AV) to the efferent branchial vessel (EV). The blood filling every interior space of the ctenidial plate flew from AV to EV and the blood flow in the ctenidium and the water flow, which was generated by the lateral cilia, on the ctenidium were in opposite directions.