Translation 2816

,a • 48'
2. Cells are oval to spherical; rhomboid plate is small,
and longitudinal groove is nearly straight; hyaline crests are
usually absent. . . . . • •' • o • • o • • • • • • • P. Volzi]. 2r
J.. Cells have a regular outline and appear more or less
(199)
elliptical in cross section,. The epivalve is larger than the hypovalve.'The
longitudinal groove extends far onto the epivalve.
P. cinctum 1.
2. Cells are more or less gibbous, circular or very slightly
elliptical in cross section; the epivalve and the hypovalve are
approximately the same size; the longitudinal groove extends very
little onto the epivalve. . . . . . . . .. . . • • P.- Zatur.ense 2.
3. Cells are very dis.tinctl,y flatteneçi dorsiventrally;
ventral plates are frequently concave, left dorsal apical plate
(M 2a) frequently quâdrangularo . . . . . . . . . P. palustre 3.
1. Cells ovoid, 30-55/t{ in length; apical panelling is
(205).
irregularly symmetrical, plates frequently concave, diffusely punctâte;
the intercalary striation is ti•ride, concave, vrithout cross
striation; the antapical plates bear
numerous spines.
P. palatinum 1.
2. Cells ovoid, 35-45 ^{ in length; apical panelling is
regularly synunetrical; plates are convex; intercalary striation is
cross-striated. Antapical plates are not spinose.
P. pseudolaeve'2.