295 
8. Navicula firma, Ktz. (‘ Bac./ p. 92, T. xxi, 10; 
Ralfs, in ‘ Prit. Inf./ p. 909). 
Syn. — Navicula affinis, Ehr., var. Raben. Europ. Diatom., p. 
19C. 
Valve broad, elongated, linear-elliptical, gradually attenu- 
ated into subacute cuneate extremities; striae close, fine, 
transverse, reaching to the median line, considerably short- 
ened. opposite the centre, moniliform ; monilae elongated, 
irregular, imparting a wavy, silky appearance to the striae. 
Hab. Fresh water. River Coquet, Elyhaugh, May, 1869. 
Kiitzing first discovered this species in the fossil earth from 
Santa Fiore in Italy; in this deposit it is quite common. I 
have slides in my possession of a fossil deposit from Nova 
Scotia also containing it. The fossil specimens agree per- 
fectly with the recent ones found in the Coquet. Hitherto 
it has only been found in the fossil state, according to 
Rabenhorst ( f Eur. Diat./ p. 226), and is now added to our 
recent British species. Navicula firma, Smith ('Synop. Brit. 
Diat./ vol. i, p. 48, pi. xvi, 138), is quite a distinct species, 
and justlv referred by Mr. Ralfs to N. microstoma, Ktz. 
(‘ Prit. Inf./ p. 909). 
The present form was described by Kiitzing as “ apertura 
media majori ; striis transversalibus nullis but this absence 
of striae is only apparent, for though somewhat difficult of 
resolution, they are very distinct when a good object-glass is 
employed. It is readily distinguished from N. microstoma, 
N. amphigomphus, and other allied forms, by the large 
central blank area, and by its punctate wavy, silky-looking 
striae. 
9. Navicula stauroptera, Ehr. 
Syn. — Stauroptera parva, Ehr. Amer., 1843, p. 135, t. iii, 1, 
19. Slauroneis parva, Kutz. ‘Bac.,’ p. 100, t. xxix, 
23. Stauroptera parva , Raben. Siissw. Diat. p. 49, 
t. ix, 6, and Pinnularia stauroptera, Raben. * Eur. 
Diat.’ p. 222. Pinnularia divergcns, var. Greg. Q. 
M. J., ii, p. 99, pi. iv, 15. Navicula parva, Ralfs, 
‘ Prit. Inf./ p. 897. 
Frustule small ; valve linear, slightly constricted near the 
broad rounded extremities ; striae oblique, 28 to 32 in 
•001", not reaching to the median line, gradually shortened 
towards the centre, and finally interrupted, leaving a central 
cruciform blank area, with four incurved sides, and reaching 
to the margin. 
