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AMPHORA. I2 5
GENUS I. AMPHORA EHR, 1831.
Frustules generally free, solitary, oval, oblong, elliptic
I bis
oval or
sub-quadrangular, often inflated or constricted in the girdle view.
Valves cymbifurm, with central
nodule marginal or sub-marginal,
often dilated into a stauros, raphe
often inflated. Connecting
zone often
longitudinally striate, plicate, or
punctate.
Endochrome formed by a single
layer, the middle of which rests on
the dorsal, connecting zone, and
ra covers over the two adjacent valves
and the other side of the zone, in
the middle of which is found the
line of separation.
A large number of Amphora are
" complex." Those are so named whose
connecting zone contains a more or
less considerable number of cuneate seg-
ments which have been, somewhat justly,
compared to slices of melon. These
segments have sometimes a structure or striation analogous to that o
the exterior segments (valves) but have neither raphe nor nodules ;
at other times however the striation of the interior segments is
different.
Fig. 24.
a Diagrammatic section of Amphora.
b Amphora ajfinis, valve view.
c Amphora ovalis, girdle view.
The genus Amphora is one of the most difficult genera of diatoms,
and it is also one of the most extensive, as authors have placed in it
more than 200 species. Prof. H. L. Smith was the first to elucidate
the structure of Amphora by demonstrating that the genus originated
from Cymbella by the unequal development of the two sides of
the connecting zone. Figure 24 a is a diagrammatic
section of an
Amphora showing at the same time the disposition of the layer of
endochrome.
In the arrangement, in this Work, of the genus Amphora, the classifi-
cation of Prof. Cleve has been followed. The sub-genera and the list of
species are given in accordance with the manuscript documents kindly lent by
the learned Professor. 4j
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