From the introduction:
"For this study, 350 samples were collected from permanent and temporary ponds, permanent and intermittent streams, rivers, lakes and marshes (Nuttall, 1970). 315 samples contained one or more species of ostracods. Samples were taken regularly throughout the year from four localities in Waterloo County. Nearly all other localities in southern Ontario were sampled more than once in the year (Figure 1). The majority of samples were collected during 1968 and 1969. The key is based on easily discernible characters of adults. Drawings were made from slide mounts using a camera lucida. Although all the species recorded in this study have been described no simple illustrated key is available for the freshwater ostracods of Ontario. The present key and illustrations should fill this gap and enable quick and reliable species diagnosis."