NAVICULA MAXIMA. Gi 
Navicula excentrica, Grun. in Wien. Verh. 1860, p. 545, t. i. fig. 1, 
Navicula bicuneata, Grun. in Wien. Verh. 1860, p. 546, t. i. fig. 4; 
Rabenh. Europ. Diat. p. 206. 
Navicula Liber, Smith, var.b. forma major, Rabenh, Europ, Diat. p. 180. 
Plate IX. fig. 4, 
Frustule large, on M. V. oblong, constricted in the middle, 
angles rounded, ends truncate. V. linear, or sublinear 
with a gentle sinuous constriction in the middle, extre- 
mities cuneate, obtuse; strie transverse, reaching to 
the median line, fine, about 45 in -001", crossed by 
one or two longitudinal lines extending between the 
apices. 
Much confusion prevails concerning this species, which 
was first discovered by Prof. Gregory in the Glenshira sand, 
and described in his papers on this deposit (Joc. cit.) ; un- 
fortunately, he subsequently described and figured N. Liber, 
Sm., as the typical N. maxima, and reduced the original 
form which he had so named to a variety. Grunow in 
1860 (op. cit.) made two new species of Gregory’s original 
N. maxima ; these he named N. excentrica and N. bicuneata ; 
but afterwards, in 1863, he reduced them to synonyms of 
N. Liber, the striz of which he estimates at from 40 to 52 
in :001"—a range of variation, however, which certainly 
does not prevail in any known species. Rabenhorst (op. 
cit.) retained Grunow’s N. bicuneata, but referred his N. 
excentrica to N. Liber, as a large variety (forma major), 
notwithstanding the authority of the latter that both are 
identical. The specimen figured in the present work is 
from the estuary of the Clyde, and supplied to me by the 
late Prof. Gregory. 
Hab. Marine. Glenshira sand, Lamlash Bay, Isle of 
Arran, and Estuary of the Clyde (Prof. Gregory). This 
species also occurs in the Mediterranean and Adriatic. 
