AS NAVICULES. 
it much resembles in size and outline, by its conspicuous 
costate strie radiating from the middle of each lobe. 
Kiitzing’s figure is very characteristic. Rabenhorst by his 
description appears to have confounded it with N. Apis. 
Hab. Brackish water. Estuary of River Coquet, North- 
umberland (A. S. D.). 
Navicula Apis, Ehrenberg. 
Navicula Apis, Ehren. Amer, p. 182, t. III. vii. fig. 18; Kiitz. Bac. 
p. 100, t. xxviii. fig. 76; Rabenh. Stissw. Diat. p. 46, pl. vi. 
fig. 28; Ralfs, in Prit. Inf. p. 894. 
Navicula didyma, var., Sm. Synop. vol. i. p. 58, pl. xvii. fig. 1544’; 
Ralfs, in Prit. Inf. pl. vii. fig. 61; Rabenh. Europ. Diat. p. 203. 
Navicula interrupta, Kiitz.; Rabenh. Europ. Diat. p. 205. 
Plate VII. fig. 3. 
V. deeply constricted into two oval or suborbicular lobes ; 
strie nearly transverse, granular, about 26 in ‘001"; 
outer section conspicuous, inner narrow, faint, and 
linear; median line broad. 
The utmost confusion prevails concerning this species, 
which nevertheless possesses very definite and distinctive 
characters. The original figures and descriptions of it by 
Ehrenberg and Kiitzing represent the strize to be parallel 
and granular, and the valve.to be constricted into two 
nearly semiorbicular lobes (‘‘media in partes duas fere 
semiorbiculares constricta, apicibus obtusis, pinnulis aspe- 
ris”). The late Prof. Smith unfortunately described it and 
N. interrupta, Kiitz., as synonymous with and constituting 
an ordinary form of N. didyma, Ehren. Rabenhorst 
(Europ. Diat.) refers N. Apis to N. didyma as a variety 
with subparallel strie, and evidently confounds it with N. 
interrupta, Kiitz., which he erroneously describes as having 
granular subradiating strie ; this description is not appli- 
