This paper is the first comprehensive review of the littoral freshwater Chydoridae (Branchiopoda, Anomopoda) of Ireland. It reports on a countrywide survey. during which a total of 316 samples was taken at 287 sampling sites between March, 1984 and June, 1986. Together with all previous records, the survey results provide baseline data on the ecology and distribution of this important animal group. A total of 41 taxa in 18 genera of the Family Chydoridae has been recorded in Ireland. Several taxa exhibit morphological differences from original descriptions and populations from other geographical regions, and the taxonomic significance of this variation is assessed. All the taxa encountered during this survey are illustrated by scanning electron micrographs. The distribution of each taxon is given and observations are made on regional trends.
