70 NAVICULER. 
costate, convergent around the central nodule, 18 in 
001". 
Hab. Fresh water : common in lakes, ponds, and ditches, 
Loch-Oich deposit, abundant. This species is much more 
lacustrine in its habitat than the two preceding species. 
Navicula Tabellaria, Ehrenberg. 
Pinnularia Tabellaria, Ehren. Amer. t. IL, i. fig. 26, II. i. fig. 7, iii. fig. 6, 
iv. fig. 5, IV. i. fig. 4. : 
Pinnularia acrospheria, Rabenh, Siissw. Diat. p. 45, t. vi. fig. 36, 
Pinnularia leptogongyla, Ehren, Mikrogeo. figg. permult; Rabenh, 
Europ. Diat. p. 188, 
Navicula leptogongyla, Ehren. Amer. 1848, p. 180. 
Navicula acrospheria, Kiitz. Bac. p. 97, t. 5. fig. 2; Ralfs, in Prit, Inf. 
p- 896. 
Plate XII. fig. 4. 
Frustule smallish, elongated. V. rather narrow, linear, 
slightly bulging in the middle and gently rounded at 
the extremities ; strize reaching near to the median line, 
obliquely inclined and gradually shortened around the 
central nodule, 22 in -001". 
This is the Pinnularia Tabellaria of Ehrenb. and the 
Navicula acrospheria of Kiitzing, concerning both of 
which species the greatest confusion has prevailed. (See 
Note to Nav. acrospheria). 
Hab, Fresh water, frequent in hilly and mountainous 
districts. Cheviots, Northumberland (4. S. D.); Scot- 
tish Highlands. ‘Loch-Oich deposit, Lough-Mourne de- 
posit, &e. 
Navicula gibba, Ehrenberg. 
Stauroptera gibba, Ehren. Amer. p. 135, t. 1. ii. fig. 3; Rabenh., Siissw. 
Diat. p. 49, t. ix. fig. 3. 
Stauroneis gibba, Kiitz. Bac. p. 107, t. xxix. fig. 24; Ralfs, in Prit. Inf 
p. 914. 
