On the Classification of the Diatomacese. By M. Paul Petit. 67 
the end of the lac d’Enghien nor on the type specimen of Moller. 
The quincuncial disposition of the puncta as indicated by Herr 
G-runow * is the only thing I have been able to verify. [In my 
own gatherings of this species the blank space is not invariably pre- 
sent, and I have doubts whether the smooth space really exists. 
I frequently find that a slight change of focus renders the striae 
visible, as in N. Isevissima Ktz., and N. crucicula Donkin' = 
Stauroneis crucicula Sm. The one-sided blank space is constant on 
the valves of N. bohemica and sculpta Ehr. = N. tumens Sm., but 
the pseudo (?) blank space on N. spheerophora seems to be caused 
by a slight depression in the surface of the valves. — F. K.] 
Genera, Navicula ( Schizonema ), Pleurosigma, Scoliopleura, 
Stauroneis. 
5th Tribe, Amphiprork®. 
The tribe of Amphiproreae only in some degree form a section of 
the Naviculeae. The disposition of the endochrome is the same, the 
presence of keels on the surface of the valves constituting the 
difference. I unite in this tribe the Amphipleurae, Plagiotropideae, 
and the Amphitropideae of Dr. Pfitzer,t the arrangement of the 
endochrome being the same in the three groups, and the sole 
difference consists in the number and position of the keels. 
The connection with the tribe of Nitzschieae is established 
through Amphiprora paludosa W. Sm., a species presenting a very 
curious organization, and for which Dr. Pfitzer has created a special 
group. 
The f. v. of this species is in the form of a figure of 8, and 
is twisted in such a fashion that half of the lower half is at right 
angles with the upper, and the valves are so reflexed that only a 
small space exists between the two sides of the zone. One can 
comprehend that the two portions of the endochrome are united 
between them, and that the eye cannot detect a single layer. It is 
in consequence of this abnormal disposition that Dr. Pfitzer sepa- 
rates A. paludosa W. Sm., from the other species. Whilst I have 
only found a single modification of the endochrome forming a con- 
necting link with a group of the Nitzschieae in which the endochrome 
forms a single layer placed diagonally in the frustule (Fig. 13, 
PL CLXXXVII.). 
Genera, Amphipleura, Berlceleya, Amphiprora. 
[The following is Ehrenberg’s description of A. pellucida in 
the ‘ Infusionsthierchen ’ : 
“ Navicula ? pellucida, gefurchtes Schiffchen, tafel xiii., fig. 3. 
* Grunow, ‘ Verhandlung in Wien,’ 1860, p. 540. 
t Rabenhorst constructed what he supposed to be a new genus to receive 
A. paludosa , A. alata, A. duplex, and A. giijantea. This he called Amphicampa 
(‘ Flor. Europ.’ p. 257), quite forgetting that he had at p. 75 described Ehrenberg’s 
genus Amphicampa. He afterwards changed it to Amphitropis. 
