A series of 50 male and 42 female mites of the prostigmatid family Tydeidae from the maritime Antarctic were each scored for 67 morphological characters. Ordination of each data set clearly showed the generic groupings described by André (1980).
The genera Pretriophtydeus, Paratriophtydeus and Paratydaeolus all appear to be monospecific in maritime Antarctica. Multivariate analysis of the data for the mites in the genus Apotriophtydeus indicated one distinct cluster as well as two diffuse clusters: these clusters are taken to represent three species. Whilst one species, named A. terrorn.sp., is easily recognized, the other two species, A. scotian.sp. and A. penolan.sp., are considered to be sibling species that are only clearly separable by the use of multivariate statistical techniques. Full descriptions of the new taxa are given, as well as a discussion of their geographical ranges and habitat preferences. Pretriophtydeus tilbrooki is also redescribed.