Translation 2816

52
1. Cell outline is pentangular, cells are slightly
(236)
flattened. Epivalve with 11 plates. There are long thorn-like
structures on the antapical plates; plates are not areolated. There is
no median apical plate P. Lindemanni 1.
2. Cells are pentangular, hardly flattened, measuring
18-25 x 15-28/A. Thorn-like structures are short, and arranged
differently on the hypovalve. Plates with longitudinal rows of
points. A median apical plate is present. The epivalve usually has
12 plates P. Viguieri 2.
1. Cells 30-40,4 in length, with pentangular outline.
(237)
Longitudinal groove widens very distinctly towards the posterioro
.Plates are concave, frequently with thorn-like structures on the
antapical plates P ElDatiewskyi 1.
2. Cells 22-25M in length, with pentangular outline.
Longitudinal groove widens very distinctly towards the posterior.
Plates are concave, frequently with thorn-like structures on the
apical plates P. pygmaeum 2.
In the Elnatiewskyi group and subsequent groups, the
panelling pattern reaches its greatest simplicity within the genus
Peridinium. The number of plates on the epivalve has been reduced _
to the minimum of 11 to 10 plates, and even the arrangement
of the plates is of the most simple type. Four plates are grouped
around the apical pore: 1 1 -4 1 (or the rhomboid plate and three apical
plates). They are surrounded by the 7' (6) pre-equatorial plates (7" to 6").