68 NAVICULE. 
acquainted belonging to the present subsection. Prof. 
Gregory has given three figures of the S.V., which he 
regarded as var. of N. inflata and of his N. varians ; he 
appears, however, to have been unacquainted with the highly 
convex and keeled characters of the valve, and with the 
contour of the frustule on M. V., features which undoubt- 
edly establish its position in this subsection. 
Hab. Fresh water. River Coquet and Sweethope Lough, 
Northumberland (4. S. D.) ; Scotland (Prof. Gregory). 
Subsection II. Valve moderately convex, not compressed laterally 
into a keel; frustule on M. V. linear, not constricted in the 
middle, and of equal or nearly equal breadth with the S. V. 
A. Valve linear, dilated in the middle, 
* Strie oblique, connivent. 
Navicula nobilis, Ehrenberg. 
Pinnularia nobilis, Ehren. Berl. 1840, p. 20; Rabenh. Siissw. Diat. 
p. 44, t. vi. fig. 2, Europ. Diat. p. 209; Sm. Synop. vol. i. 
p. 54, pl. xvii. fig. 161. 
Navicula nobilis, Kiitz. Bac. p. 98, t. iv. fig. 24; Ralfs, in Prit. Inf 
p- 895. 
Pinnularia mesogongyla, Ehren. Mikrogeo. t. VI. i. fig. 5. 
Plate XI. fig. 1. 
Frustule very large, elongated. V. broad, linear, slightly 
bulging in the middle and at the extremities; striz 
not reaching to the median line, stout, costate, 
obliquely inclined towards the central nodule, 13 in 
O01". 
Hab. Fresh water: common in boggy pools and ditches 
in hilly and upland districts. Lough-Mourne deposit, 
Dolgelly earth, &c. 
