68 Transactions of the Royal Microscopical Society. 
N. laevis testula lineari lanceolata aciculari utrinque sub-acuta 
longitudinaliter sulcata sulco singulo in quovis latere intercostas binis. 
Icb kenn diese Form nur aus Exemplaren, die ick von Herrn 
Kiitzing trocken erbielt. Er bat in den verkauflichen Decaden 
seiner Algen verbreitet. Sie liess sicb scharfer beobacbten, doch 
bin icb iiber die mittleren Offnungen in Zweifel geblieben. Sie bat 
einen Kieselpanzer, kann daber kein Closterium sein. Vielleicbt 
eigene Gattung. Sie fand sicb zablreicb zwiscben Oscillatorien 
und war beweglich.” 
I have examined specimens of this form from many locabties 
and several exquisite photographs by Woodward, Janiscb, and 
others, but have never been able to detect the keels ; one of the 
photos., taken with a Tolies’ immersion fg amplifying 2051 diameters, 
shows the striae reaching from margin to margin, which would not 
be the case if the valve was not perfectly flat. Ehrenberg gives 
an ideal transverse section of the frustule, and this has apparently 
misled other observers who assumed the correctness of the sectional 
view. I have also examined the figures in Ehrenberg’s ‘ Infu- 
sionsthierchen,’ Kiitzing’s ‘ Bacillarien,’ Eabenhorst’s ‘ Siisswasser 
Diatomaceen,’ and ‘ Alg. Europ.’ (the figure in the latter work 
is evidently copied from Wm. Smith’s ‘Synopsis’), Hassell’s 
‘British Fresh -water Algae,’ pi. cii. fig. 8, Pritchard’s ‘Infu- 
soria,’ 3rd and 4th edition; the figures here are copied from 
Ehrenberg and Kiitzing, excepting fig. 30, pi. iv., 4th edit., which 
is from the ‘ Synopsis,’ the last being the most unlike the form 
we call A. pellucida ; indeed, were it not that West says * that 
it is identical with Rapliidogloea micans, Kiitz. (by the way this 
is a marine species, and Kiitzing’s figures of it, although like 
A. pellucida, do not resemble that in the * Synopsis ’), I should 
be disposed to believe that the A. pellucida of the ‘ Synopsis ’ is 
not the A. pellucida of other authors. It is remarkable that 
none of the engraved figures bear the slightest resemblance to the 
actual form, and that the curious median line, with its spatulate 
terminal expansions distinctly visible even with a single lens 
magnifying 60 diameters, should not only have been overlooked 
by the earlier observers, but also by the Bev. W. Smith, who 
sometimes used a Smith and Be*k |th objective. The sub-marginal 
dots of course only existed in the draughtsman’s imagination. 
Schumann’s figure! is fairly like this species, but represents the 
striae as composed of puncta arranged in squares about 15 or 
16 in -001"!!! 
In a communication received (1864) from Professor W. Arnott, 
he says, “ Not one species (of Ampliipleura) has longitudinal ribs or 
costae ; even on the trustifies what have been mistaken for them in 
A. pellucida are the median lines and two margins of each valve, 
* Pritchard, 4tli edit., p. 925. 
f ‘ Die Diatomeen der Hohen Tatra,’ taf. ii. fig. 19. 
