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NAVICULA.
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A. True Naviculse. Frustules free, not enclosed in gelatinomucous
fronds.
Sub-genus
Analysis of Groups.
I. Navicula.
I. Valves without distinct puncta, furnished with costae (canaliculi) or
robust strire, having the appearance of costae ; never didymous in form.
True costre, not resolvable into beads . . . 1. Pinnularise.
Striae robust, having the appearance of costae but resolvable into beads;
Radiosse.
strice radiate, almost or quite reaching to the raphe . . .2.
II. Valves with very distinct puncta or fine striae having
to costae or with costae ; or again with costae alternating with rows of beads.
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Valves
without
any
appearance
of
stauros.
Valves
with
puncta
not
forming
longitudinal
lines
in
zig-zag.
Striae
with
beads not
forming
longitudinal
lines.
Striae
with
beads
forming
longitudinal
and
transverse
lines.
Striae
i6-
no semblance
a. Valves wit/i strne interrupted by two sulci near the raphe.
{ ( Valves more or less constricted in the
Sulci not median j portion
lvre
Sulci -|
straight. - s haped. \ ya i ves without constriction in the median
I portion ....
I Sulci lyre-shaped ......
L Sulci very broad and occupying the greater portion of the valv^
b. Valves more or less lanceolate, or elliptic or linear lancvlate, without any sulcus.
3. Didymse.
4. Ellipticse.
5. Lyratse.
(J. Hennedyjse.
f
Valves having the appear- f Valves having the appearance of a
ance of a stauros, either | grater, with very large, elongated
by the absence of striae or beads .... 7.
-{ Asperse.
by the space between j
them . . . t Valves with tine striae .
8. Stauroneidese.
leaving
a con-
Hyaline space very
elongate and insiderable
hyaline
finitesimallyminuate
.
di-
space !
round Hyaline space
the raphe rounded and
and abruptly
central
nodule.
Beads extending over the whole
valve ....
diminu-
9. Palpebrales.
ate
10. Abbreviate.
11. Perstriatse.
Valve very elongate,
linear .
Valve lanceolate .
almost
12.
13.
Johnsoniese.
Crassinerves.
Valves
with
puncta
forming
longitudinal
lines
in
zig-zag.
Striation almost invisible with the best objectives, valve linear lanceolate
^ simulating an Zig-zags interrupted by pale places where the
valve is . . . depressed .14. Sculptese.
Lines in zig-zag, regular, not . interrupted 15. Serian'eEe.
Amphipleura....... \3bis. Fusiformes.