Gubernaculum:

An accessory male copulatory piece which is formed by sclerotization of the dorsal wall of the spicule pouch,variable in shape but generally with incurved margins(Anderson 1974)(Y-shaped in Dichelyne(Cucullanellus)sciaenidicola,Cucullanus orbignianus(Nematoda:Cucullanidae))(Timi 2006)

 In nematodes,A protuberance on the wall of cloaca. It apparently guides the spicule during copulation