 The onefin electric ray or Cape numbfish ( Narke capensis ) is a common but little @-@ known species of electric ray in the family Narkidae , native to South Africa and Namibia . It is a benthic fish found in shallow coastal bays over sandy or muddy bottoms . This small species reaches 38 cm ( 15 in ) in length , and has a nearly circular pectoral fin disc and a short , muscular tail that supports a large caudal fin . It can be identified by its single dorsal fin , which is located over the large pelvic fins . Its dorsal coloration is yellowish to dusky brown . 
