294 
tains several distinct species, some of them already described 
as N. tumida, oblonga, peregrina, acuta , radiosa, and scutel- 
loides ; and amongst them the present form, which remains 
undescribed, although apparently delineated in figs. 14, 15, 
and 25 in Professor Gregory’s plate. 
Hab. Fresh water. River Coquet, Elyhaugh. Abundant, 
April and May, 1869. The typical N. oblonga was abundant 
in the same gatherings, 
6. Navicula Cymbula, Donkin. 
Syn. — Navicula varians, Greg., ‘Trans. Micr. Soc.,’ vol. iii, pi. 
ii, 33. 
Yalve elongated, elliptical-lanceolate, gradually attenuated 
towards the elongated acute extremities ; striae robust, 
obliquely inclined towards the centre, but becoming gradually 
direct, much coarser, and much more distant opposite the 
centre ; reaching the median line, and slightly shortened 
around the centre. 
Hab. Fresh water. River Coquet, Elyhaugh, plentiful, 
April and May, 1869. 
7. Navicula limosa, Ktz. ‘ Bac./ p. 101, T. iii. 50; 
Grunow in ‘Wien. Verh./ 1860, p. 544, T. iii. 8; 
Raben. Siissw/ D., p. 41 ; T. vi. 31 ; and ‘ Europ. 
Diat.,’ p. 188. Ralfs in ‘ Prit. Inf./ p. 894. 
Frustule small. Yalve very convex, narrow, linear elon- 
gated, with two marginal sinuous constrictions, . and three 
inflations ; one central, and two terminal ; the central gene- 
rally the larger ; extremities sub-cuneate, obtuse ; striae 
delicate, transverse, dry valve yellowish brown. 
Rabenhorst (‘ Eur. Diat./ p. 189) refers the three 
following forms to this species as varieties : — Navicula 
Gibberula, Ktz. (‘ Bac./ p. 101, T. iii, 50*) ; N. inflata, 
Grun. (‘Wien. Verh./ 1860, T. iii, 8. c.)=N. Gibberula, 
Sm. (‘ Svn./ vol. i, p. 51, pi. xvii. 160) ; N. bicuneata, 
Grun. (loc. cit., fig. 7). 
The longitudinal striae described by Rabenhorst are 
deceptive appearances produced by the convexity of the 
valve. 
Hab. Fresh water. River Breamish, Ingram. River 
Coquet, Elyhaugh, plentiful; near Hull, very scarce. Mr. 
Norman. 
I have been induced to give a description and figure of 
this species, as it is new to Britain. 
