Not valid. The original description was from a specimen recovered from swordfish (Xiphias) in the Mediterranean Sea. Pennella tridentata is identical with many specimens of P. filosa (also found on swordfish) in size and external morphology. Listowsky’s specimen exhibited three holdfast horns (two lateral, one dorsal) a condition often found in P. filosa. There is nothing in the original account which serves to differentiate P. tridentata from a variable form of P. filosa. Synonym of P. filosa.