The Protozoa of New Zealand Intertidal Zone Fishes Marshall Laird, M.Sc., Ph.D. Department of Zoology, Victoria University College, Wellington [Read before a meeting of the Wellington Branch, July 23, 1952; received by the Editor, August 1, 1952.] Abstract Fourteen species of Protozoa are recorded from 458 New Zealand intertidal zone fishes of 10 species. Haemogregarina bigcmina Laveran and Mesnil (Sporozoa: Coccidia) is reported from 5 new hosts, Oliverichtus melobesia (Phillipps) (Gobiesocidae), Ericentrus rubrus (Hutton), Tripterygion varium (Forster), T. medium Günther and Notoclinus fenestratus (Forster) (Blennidae). Myxidium incurvatum Thélohan (Sporozoa: Myxosporidia) is recorded from 4 new hosts, the clingfishes Diplocrepis puniceus (Richardson) and Oliverichtus melobesia, the blenny Notoclinus fenestratus, and Acanthoclinus quadridactylus (Forster) (Acanthoclinidae). Ericentrus rubrus is listed as a new host for Trypanosoma tripterygium Laird (Mastigophora: Protomonadina). Two new genera are established. The generic designation Davisia is proposed for certain Myxosporidia previously included in Ceratomyxa Thélohan and Sinuolinea Davis, with Davisia (= Ceratomyxa) spinosa (Davis, 1917) as the genotype. A unique peritrichous ciliate belonging to Kahl's family Scyphidiidae is described as the type of a new genus. Caliperia. An undetermined species of the myxosporidian genus Zschokkella is recorded from the urinary bladder of Tripterygion varium, and the following new species are described:— Haemogregarina (Hepatozoon?) acanthoclini (Sporozoa. Coccidia)—blood of Acanthoclinus quadridactylus. Leptotheca subelegans (Sporozoa: Myxosporidia)—gall bladder of Callogobius atratus (Gobiidae) and Diplocrepis puniceus. Davisia diplocrepis (Sporozoa: Myxosporidia)—urinary bladder of Diplocrepis puniceus. Sphaeromyxa tripterygii (Sporozoa: Myxosporidia)—gall bladder of Tripterygion varium and T. medium Myxosoma tripterygii (Sporozoa: Myxosporidia)—subdermal connective tissue of Tripterygion varium. Scyphidia (Gerda) acanthoclini (Ciliata: Peritricha)—gills of Acanthoclinus quadridactylus. Caliperia longipes (Ciliata: Peritricha)—gills of Oliverichtus melobesia and Ericentrus rubrus. Trichodina (Trichodina) parabranchicola (Ciliata: Peritricha)—gills of Diplocrepis puniceus, Oliverichtus melobesia, Acanthoclinus quadridactylus, Acanthoclinus trilineatus Griffin, Ericentrus rubrus, Tripterygion varium, T. medium and Notoclinus fenestratus (the dominant trichodinid on the first four hosts). Trichodina (Trichodina) multidentis (Ciliata: Peritricha)—not recorded from O. melobesia, but otherwise host list as for T. parabranchicola, over which it is dominant on the last four hosts. Trichodina (Trichodina) multidentis n.sp. is a new host for the endoparasitic suctorian Endosphaera englemanni Entz. The affinities of these protozoans are discussed, with particular regard to species already recorded from intertidal zone fishes in other parts of the world. Consideration is given to the problem of host specificity in relation to host habitat. The evidence suggests that the environmental niche occupied by fishes is a most important factor in determining the composition of their protozoan fauna.