58 NAVICULEZ. 
its valve, with the characters assigned to Sec. II.; but in 
other respects it is quite conformable: its valves are highly 
convex and keeled, and its frustule on M. V. is broad and 
constricted, showing its proper position to be in the present 
subsection. 
Hab. Marine. Tynemouth sands Northumberland, 
South-Shields sands (A. 8. D.) ; Clyde (Prof. Gregory). 
B. Valve rhomboid or linear ; stri@ fine, transverse, and parallel, or 
nearly so, reaching to the median line. 
Navicula rhombica, Gregory. 
Navicula rhombica, Greg. Quart. Mier. Journ. vol. iii. p. 40, pl. iv. 
fig. 16, and Trans. Micr. Soc. n. 8, vol. iv. p. 38, pl. v. fig. 1; 
Ralfs, in Prit. Inf. p. 908, pl. vii. fig. 71; Rabenh. Europ. 
Diat. p. 181. 
Navicula Inbellus, Greg. Diat. of the Clyde, p. 57, pl. vi. fig. 101; Ralts, 
in Prit, Inf. p. 904; Rabenh. Europ, Diat. p. 172. 
\ 
\ 
Plate IX. figs. la & 16, 
Frustule on M. V. broad, quadrate, slightly constricted in 
the middle, angles slightly rounded, extremities trun- 
cate ; connecting zone traversed by longitudinal lines. 
V. hyaline, rhombic, or elliptical-lanceolate, with sub- 
acute or obtuse extremities; striz fine, about 45 in 
001", reaching to the median line, nearly transverse, 
but slightly connivent and more opaque and distinct 
around the central nodule. 
Hab. Salt water. Glenshira sand and Tantallon, Had- 
dingtonshire ; Estuary of the Clyde (Prof. Gregory); New- 
biggin, Northumberland (A. S. D.). 
