They have seven gill openings on each  side, a single nostril on the upper part of the head, and, in place  of jaws, an oral sucking disc bearing teeth and a rasplike tongue.  
These eel-shaped members of family Petromyzontidae do  not have paired fins, but they do have a notochord, a tail fin and  one or two dorsal fins. They have seven gill openings on each  side, a single nostril on the upper part of the head, and, in place  of jaws, an oral sucking disc bearing teeth and a rasplike tongue.  FTP, name these parasitic aquatic animals which feed by attaching  themselves to larger fish.
These eel-shaped members of family Petromyzontidae do  not have paired fins, but they do have a notochord, a tail fin and  one or two dorsal fins.
{lamprey}  (do not accept remora, of family Echeneididae, which does have a  spine)