Evolutionary and Systematic Relationships in the Flagellate Order Trichomonadida Kirby*

SYNOPSIS. Discussion of the systematic relationships and of the evolutionary trends among the 4 families, Monocerco‐monadidae, Devescovinidae, Calonymphidae, and Trichomonadidae of the order Trichomonadida includes a consideration of 8 subfamilies, 3 of them new. The genera of Devescovinidae and Calonymphidae, all of which are limited in their distribution to lower termites, are not considered; those of Monocercomonadidae and Trichomonadidae are discussed in the light of the information pertaining to their structure, morphogenesis, distribution, and host‐parasite relationship. Diagnoses are given for 6 subfamilies and 14 genera belonging to the latter two families, which are diagnosed also. Type genera are designated for each family and subfamily that is discussed, and type species are designated for each of the 14 genera. A complete synonymy is presented for each type species. Two new species, one of Monocercomonas and another of Tritrichomonas are named and diagnosed. The paper includes a key to all the families and subfamilies of the order and to the genera of Monocercomonadidae and Trichomonadidae.