Cyst-theca Relationships in Scrippsiella (Dinophyceae) and Related Orthoperidinioid Genera

Study of sediments from Loch Creran, a Scottish west coast sea-loch has yielded four new species of small calcareous dinoflagellate cysts. Single cyst incubation techniques and culture studies have shown all these to be members of the genus Scrippsiella Balech ex Loeblich. Descriptions are given of both the motile stage and cyst of these new species, (S. crystallina, S. lachcrymosa, S. trifida). These are compared with descriptions of S. trochoidea and Pentapharsodinium dalei. The archeopyle of Scrippsiella is theropylic and is interpreted as representing the loss of 2‘—4’.and 1 —3a paraplates, the operculum remaining attached to the cyst body by the first apical paraplate.