Family ENTORHIPIDIIDAE Madsen, 1931

Body large, flattened laterally, posterior end tapered to tail; dense, uniform somatic ciliation, with single caudal cilium; oral area, with two well-developed membranelles, overhung by frontal lobe of body; inquilinic in widely distributed species of sea urchins, algivorous within host intestine.

Entorhipidium Lynch, 1929. Several species.