This work constitutes a first contribution to the taxonomy of dinoflagellate resting cysts in planktonic samples of this region, being studied nine species of Protoperidinium Bergh and Zybabikodinium Loeblich Jr. et Loeblich III of the family Peridiniaceae. Incubation experiments with living material and parental thecae containing resting cysts in fixed samples allowed setting up of the cyst-theca relationship in P. obtusum (Karst.) Parke et Dodge, and also that verification for P. excentricum (Pauls.) Bal., P. claudicans (Pauls.) Bal., P. oblongum (Aur.) Parke et Dodge and Z. lanticalatum Loeb. Jr. et Loeb. III. P. conicides (Pauls.) Bal., P. antcuiciticum (Schimp.) Bal. P. pentagonum (Gran) Bal. and P. compressum (Abe) Bal. cysts were ' studied offering also an analysis for thecal sulcal plates for the latter species. Geographic distribution and temperature and salinity data for samples with living cysts are given.
Dinoflagellata; Cysts; Taxonomy; Geographical distribution; Protoperidinium; Zygabikodinium; Southwestern Atlantic