422 Mr. C. Mereschkowsky on Okedenia, ul. 
their valves, as well as the structure of the connecting-zone, 
only confirms, as we have already seen, their relationship. 
Thus, if all the above facts are taken into consideration, we 
cannot but believe in the re-establishment of the old genus 
Okedenia ; its inner structure is so peculiar and so different 
from all other Naviculoid Diatoms that it seems necessary to 
separate it as a distinet family—the Okedemie. 
‘The diagnosis of the genus Okedenia in its new sense is 
as follows :— 
OKEDENIA, Eul., s. emend. 
Valve elongated, very narrow, linear, often inflated in the 
middle and at the extremities, straight and symmetric or 
arcuate and asymmetric, terminal nodules usually distant from 
the margin, strie fine (18-24 in 0:01 mm.), connecting-cone 
complex. Endochrome composed of numerous chromato- 
phores, from 4 to 38, usually of the shape of the letter H, 
sometimes rounded, disposed in pairs along the connecting- 
zone, rarely along the valves, with a central pyrenoid usually 
common to each pair. 
Analytical Key to the Species and Varieties of the 
Genus Okedenia (s. emend.). 
Valve symmetric, straight. 
Valve inflated in the middle and at the 
ends. 
Length 0:1-0:260 mm., breadth 0-009- 
0-016 mm.; strive 18-20 ........ O. scopulorum (Bréb.), Mer. 
Length 0°33-0-4 mm., breadth 0-007 
MIR GUMes IU ey giggadc'o ddlne op 6 O. scopulorum, var. perlonga 
Length 0:06-0:07 mm., breadth [(Brun), Mer. 
0:0075 mm. ; strize 24 .......... O. scopulorum, var. belgica 
Length 0:0427 mm., breadth 0:0024 [(V. H.), Mer. 
mm.; 8 (?) chromatophores...... O. scopulorum, var. delica- 
Valve linear, not inflated; length 0:072- [tula, Mer. 
0120 mm., breadth 0-0062-0:0067 
mm.; strie 16-18; 10 chromato- 
phores without horns ........... . O. scopulorum, var. fascrcu- 
Valve asymmetric, arcuate. [data (Gr.), Mer. 
Chromatophores along the connecting- 
zones; ventral margin of the valve 
strongly concave. 
4 chromatophores with long straight 
horns; length of the frustule 0 0v0- 
0:150 mm.; connecting-zone nar- 
HO) Gio iiss whe Bs ehoiele hisiel djeloiei vais O. inflexa (Bréb.), Kul. 
8 chromatophores with short undulated 
horns; length of the frustule 0:075 
mm. ; connecting-zone broad .... O. pontica, Mer. 
