POLYDINIINAE (p.502), n. subf. of Ophryosco-lecidae, is proposed to include POLYDINIUM (p.502), with P. mysoreum* (p.502); and ELEPHANTOPHILUS (p.504), with E. zeta* (p.504), from the caecum and colon of the Indian elephant. The subfamily manifests the highest orthogenetic phase in the family. Metamerism is shown by repetition along the major axis of motor and excretory organelles; bilateral symmetry is indicated by flattening of the esophagus and division of the added membranelles; and there is also dorso-ventral differentiation. In the Proboscidea the evolution of the host and that of its parasites are coincident processes and are comparable in direction.