Mr, ©. Mereschkowsky on Okedenia, Zul. 415 
LI.—On Okedenia, Hul. 
By C. Merrescukowsky. 
[Plate VIL] 
THE genus Okedenia was established in 1868 by Hulen- 
stein in a manuscript which was never published. He 
founded it for a strange and particular diatom which had 
been described in the year 18£9 by Brébisson under the name 
of Amphipleura inflexca*; and for some time this genus 
was accepted by such authorities as Cleve and Van Heurck, 
who both published among their type species the Amphi- 
pleura infleca of Brébisson under the name of Okedenia 
inflexa t. A more careful examination of the structure of the 
frustule made especially by Van Heurck has convinced this 
author, Cleve, and, finally, all diatomists that the form 
was simply an Amphora, an opinion which had already been 
suggested by H. L. Smith in 1873 f. ‘Thus this genus had 
only a short existence, and was soon discarded, as it seemed, 
for ever. 
In the present note I shall endeavour to restore this oll 
genus and establish it on a new basis. It will, however, 
comprise not only Amphora inflexa, but also another rather 
curious and strange diatom belonging to the genus Navicula. 
I mean N. scopulorum, Bréb., or N. Johnsonit (W. Sm.) as 
some authors prefer to call it. Both are very peculiar forms, 
not near akin to any other species of the respective genera to 
which they have been assigned; and this has struck all 
diatomists who have had to deal with them. ‘Thus, for in- 
stance, Cleve calls Amphora inflexa an ‘isolated and strange 
form” §, and in regard to Navicula scopulorum he says that 
“it is a very characteristic form, which seems not to be very 
nearly allied to any other species” ||; and Van Heurck {| has 
even created a special group for this species—the Johnsoniz. 
As may be seen, the shells alone point to the fact that these 
diatoms are of a very peculiar nature, distinct from Navicula 
as well as from Amphora. 
But it is not so much on account of the form and structure 
* Kutzing, Spec. Algarum, p. 88. 
+ Cleve, Mar. D. no. 192; Van Heurck, type no. 167. 
t ‘The Lens’ (Chicago), ii. p. 78. 
§ Cleve, Synops. of the Navicul. Diat. part ii. p. 131. 
|| Z. e. part i. p. 162. 
4] Van Heurck, Syn, d. D. d. Belg. p. 99. 
