NAVICULA LATIUSCULA. 27 
acute ; strive lengthened towards the extremities and 
shortened in the middle (so as to leave a lanceolate 
blank median space), distant, oblique, costate, about 
15 in :001". 
Hab. Marine. Lamlash Bay Isle of Arran, Glenshira 
sand (Prof. Gregory). 
Navicula alpina, Smith. 
Pinnularia alpina, Smith, Synop. vol. i. p. 55, pl. xviii. fig. 168; Ra- 
benh. Europ. Diat. p. 213. 
Navicula alpina, Ralfs, in Prit. Inf. p. 906. 
Plate IV. fig. 6. 
Frustule large, on M. V. linear with truncate extremities. 
V. oblong-elliptical, or elliptical-lanceolate, with 
rounded extremities ; central nodule depressed ; striz 
shortened around the central nodule, radiate, distant, 
broad and costate, about 6 or 7 in ‘001". 
The M. V. of this species is conspicuous from the two 
longitudinal, parallel lines of transversely elongated gra- 
nules observable on the connecting zone. 
Hab. Fresh water, subalpine. Aberdeenshire (Dr. 
Dickie) ; Ben M‘Dhui (Mr. P. Grant) ; Loch-Oich deposit, 
Caledonian Canal; Cheviots, Northumberland (A. S. D.). 
Navicula latiuscula, Kiitzing. 
Navicula latiuscula, Kiitz, Bac. p. 98, t. v. fig. 40; Ralfs, in Prit, Inf. 
p- 905; Rabenh, Siissw. Diat. p, 38, t. vi. fig. 61, and Europ. 
Diat. p. 182. 
Navicula patula, Sm. Synop. vol. i. p. 49, pl. xvi. fig. 189. 
Plate IV. fig. 7. 
Frustule large. V. oblong-elliptical, or elliptical-lanceo- 
D2 
