42 NAVICULEE. 
transverse, fine, granular, about 60 in ‘OOL", shortened 
opposite the central nodule. Colour of dry valve 
brown. 
The “longitudinal striz,” as they are termed in this 
species, appear to be produced by plicz or folds on the 
surface of the valve. 
Hab. Fresh water: frequent in boggy pools in elevated, 
exposed, or subalpine localities. 
Navicula rhomboides, Ehrenberg. 
Navicula rhomboides, Ehren. Amer. 1848, t. IIT. i. fig. 15; Kiitz. Bac. 
p. 94, t. xxviii. fig. 45, and t, xxx. fig. 44; Rabenh. Siissw. 
Diat. p. 38, t.v. fig. 18, and Europ. Diat. p.171; Sm. Synop. 
vol. i. p. 46, pl. xvi. fig. 129, and vol. ii. p.90; Ralfs, in Prit. 
Inf. p. 903, 
Plate VI. fig. 11. 
V. rhomboid-lanceolate, nearly quadrangular, extremities 
slightly obtuse, or rounded ; striz fine, indistinct, 85 
in ‘001", transverse, reaching to the median line. 
Hab. Fresh water: frequent, especially in boggy pools in 
subalpine localities. 
Navicula crassinervia, De Brébisson. 
Navicula crassinervia, Bréb. in Sm. Synop. vol. i. p. 47, pl. xxxi. fig. 271; 
Ralfs, in Prit. Inf. p. 900. 
Frustulia saxonica, forma aquatica, Rabenh. Europ. Diat. p. 227. 
Plate VI. fig. 12. 
Frustule small. V. hyaline, lanceolate, gently constricted 
beneath the obtuse extremities ; strise obscure. 
Hab, Fresh water: alpine or subalpine. Snow-mud, 
Grampians (Dr. Dickie); Cheviots, Northumberland, abun- 
dant in peat-mosses in exposed situations (4. 8. D.). 
