CYMBELLA EXCISA (KUETZ.) DE TONI
Valve as in affinis, but with tumid and excised ventral margin; a punctum is found on the ventral side (not shown in the figure).
According to Cleve this is a variety of C. affinis.
Common in ponds.
Pl. [18], Figs. 15, 19?
CYMBELLA PARVA (WM. SM.) CL.
Valve semi-lanceolate, with produced apices; ventral margin slightly tumid; axial area narrow; striæ coarsely but obscurely punctate.
C. affinis and C. parva are quite variable, the latter differing by its lanceolate form and the absence of a punctum, which, however, is sometimes difficult to recognize. In a gathering of C. parva, it is quite possible to find numerous abnormal forms which appear to be sporangial, so that specific distinctions are difficult if based on occasional specimens.
Common in ponds.
Pl. [38], Fig. 14.