418 Mr. C. Mereschkowsky on Okedenia, Eul. 
The valve is characterized by its linear form, not inflated in 
the middle (or only imperceptibly) nor at the ends. 
Two or three other varieties of this species are known :— 
(1) Var. perlonga * (Brun), Mer. 
Brun, Diat. esp. nouy. p. 39, pl. xv. fig. 2; Cleve, Syn. Navic. D. part 1. 
p. 152. Navicula famelica, Castrac. Osserv. Cicloph. p. 9, according 
to De Toni. 
Length 0:33-0:40 mm., breadth of valve 0-007 mm. ; striz 
138 in 0°01 mm. 
(2) Var. belgica (V. H.), Mer. 
Navicula Johnsonii, var. belgica, Van Heurck, Syn. d. Diat. d. Belg. 
Suppl. B, fig. 29. Navicula scopulorum, var. belyica, Cleve, Syn. 
Navic. D. part i. p. 152; Peragallo, Diat. mar. d. Fr. pl. viii. fig. 27. 
Length 0:06-0:07 mm., breadth of valve 0°0075 mm. ; 
strie 24 in 0°01 mm.3; valve gibbous. 
(3) Var. delicatula, Mer. 
Finally I will mention here a very delicate and small 
form of which I have found a single specimen in San Pedro, 
California (fig. 5). The valve is very narrow, inflated in the 
middle and at the extremities, length 00427 mm., which 
agrees with the size of var. belgica, being only a little smaller ; 
but the breadth of the valve, only 0°0024 mm., is much 
smaller than in the latter (0‘0075 mm.) ; it seems therefore 
more likely to represent anew variety, which could be named 
var. delicatula, Mer. 
Unfortunately the specimen was not in a sufficiently fresh 
condition to ascertain the structure of its endochrome in all 
its details. 1 have only noticed the presence of four coloured 
masses, which probably represent eight chromatophores. 
‘This form requires further examination. 
Okedenia inflexa (Bréb.), Eul. (Pl. VII. figs. 9-11.) 
Amphipleura inflexa, Bréb., Kiitzing, Sp. Alg. p. 88. Okedenia in- 
flexa, Kul. MS., Cleve, Mar. Diat. no. 192 (1879); Van Heurck, Type 
no. 167. Amphora inflexa, H. Li. Smith, Lens, ii. p. 78, pl. ii. fig. 16 
(1873); Cleve, Syn. Navic. D. part ii. p. 181; Peragallo, Diat. mar. 
d. Fr. p- 215, pl. xlix. figs. 1,2; Van Heurck, Treat. on Diat. p. 135, 
fig. 25. 
The endochrome of this species differs very little from 
* The figure which Peragallo gives of this variety (Diat. mar. d. Fr. 
pl. viii. figs. 28, 29) does not belong to it, the valve being much too 
short. Even my fig. 1 (which could with more propriety be referred to 
yar. perlonga) is not nearly so long as the original fig. of Brun. 
