Mr. C. Mereschkowsky on Okedenia, Hul. 417 
This structure of the endo- 2. 
chrome is so different from that 
of all other species not only of 
the genus Navicula (of which I 
have studied about fifty species 
in this respect), but of all Na- 
viculoid diatoms in general, that 
there can be no doubt as to 
the systematic place of this 
diatom: it is certainly not a 
Navicula. 
I have observed a great num- 
ber of living specimens of this 
species both in the Black Sea 
and the Mediterranean (Ville- 
franche). Some of the valves 
here figured are so long and Dead shells of O. scopulorum, 
narrow that they seem to repre- with endochrome. 722 
sent an intermediate form be- 
tween the type species and the var. perlonga, Brun. 
° 
ie) 
O 
io) 
©) 
O 
O 
O 
) 
O 
O 
O 
fo) 
° 
ie) 
(eo) 
Okedenia scopulorum, var. fasciculata (Grun.), Mer. 
(Pl. VII. figs. 6-8.) 
Grunow, in Cleve, Mar. D. no. 178; Cleve, Syn. Naviec. Diat. part i. 
p. 152. 
The endochrome of this variety, of which I have observed 
only a few specimens in the Pacific Ocean (San Pedro, 
California), is in the main the same as in the type species, 
differing by the plates or granules not having the four elon- 
gated prolongations which are so characteristic of the type 
(fig. 7); in this variety the plates are quadrangular, more 
developed transversely than longitudinally, with their margins 
concave, and the two central plates alone are provided with 
short prolongations or rudiments of horns of the same kind 
as in the type. ‘The number of plates is twenty, disposed in 
five pairs in each half of the frustule, not reaching its extre- 
mities. The centre of each plate contains a round pyrenoid, 
which is not united with the pyrenoid of the opposite plate. 
The eleoplasts are numerous; there are usually two of them 
between each two plates at their ends. When seen from the 
valve-face (fig. 8) the chromatophores appear to be very 
thick, but this is probably due to the presence of pyrenoids 
and does not represent their real thickness. 
Length of the valve 0:072 mm. (according to Cleve 0:08- 
0-120 mm.), breadth 0:0062-0:0067 mm. 
Ann. & Mag. N. Hist. Ser. 7. Vol. viii. 30 
