Environmental Engineering Reference
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A
B
10 μm
Figure 4.64
Cocconeis
. Valve view of this sedimen-
tary diatom. Acid digest, lake sediment sample. Repro-
duced with permission of M. Capstick.
153
(152) (a) Cells not as broadly elliptical with
bluntly rounded ends, both valves with a
true raphe which lies within a long thick-
ened ridge. Two chloroplasts with lobed
margins, one either side of the long apical
axis.........................
Diploneis
20 μm
Figure 4.65
Cymatopleura elliptica.
(A) girdle view;
(B) valve view.
The raphe is situated between prominent
silica ridges. Striae on the valve surface
run from the raphe to the margin. Chloro-
plasts may contain a pyrenoid. Cells 20-
130 μm long, 10-60 μm wide. Widespread
in mainly oligotrophic waters on bottom
deposits, some species brackish or marine.
Bacillariophyta. Plate XXIII.
Cells are elliptical often with a central
'waist'. The valve surface is character-
istically undulate, particularly visible in
girdle view, giving it a transverse banded
appearance. The raphe is on a raised ridge
running around the valve margin. A single
large lobed chloroplast is present. Found
on bottom sediments, commonly epipelic.
Widespread and common. Cells 30 to
>200 μm in length, 20-60 μm wide. Bacil-
lariophyta. Fig. 4.65.
(b) Cells without thickened ridges along
most of the length of the raphe . .....
154
154
(153) (a) Cells with a prominent transverse
undulate surface in girdle view and banded
transverse shaded areas in valve view.
Isopolar. ................
Cymatopleura
(b) Cells without undulate surface.
Lanceolate to oval in shape, sometimes
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