RECENT RESEARCHES IN THE DIATOMACEE. 293 
The form of the cell-cover differs little, but the inner structure is 
quite different. The Amphitropis paludosa, (W. Sm.) Rab., is dis- 
tinguished by means of its sigmoid keels constructed in relation to one 
another, as in the case o Scoliopleura, as ine ae the two Ade! 
ing longitudinal strie. It has only as e endochrome-plate lying 
ral 
obvious. Whether the similarly a genera, Aagiiep rora, (Ehr.), 
and Donkinia, (Pritch.), belong to this or to the preceding group re- 
mains to be determined. Aux xospores in all these forms are still 
n g observation of our author suggests the 
propriety of subj ecting es various related forms to a careful exami- 
nation with a view to a satisfactory arrangement. 
Nitzschiee, (Grun.). 
The forms hitherto treated of agree in this cee we that, with 
the exception of the Epithemie, which have a very indistinct median 
line, they exhibit nodules and distinct median lines; Aad ¢ t the 
transverse section is rectangular or trapezoid, except jabra: 
= 
6B 
a 
i=) 
eS 
at 
7 
oe 
o 
=e 
© 
a 
=) 
=met 
possess neither oe nor median lines, at — their transverse | 
section is ever distinctly rhomboid. oup embraces three 
genera, MVitzschia, Cadtnel, and "Bai llaria. 
Nitzschia. 
which we have species of a tw ofold structure, which may be 
N. sig note eb W. Bi: N. clausii, Hantzsch—present 
the same position of the endochrome-plate, while NV. dubia, 
Hantzsch, and J. linearis, (Ag.) W. Sm., differ widely in the inner 
structure. In them the endochrome-plate passes gee across the cell, 
reaching from one row elpuncta to the othe When the frus- 
