66 NAVICULEE. 
form ; moreover it differs essentially in the structure of the 
valve and in the contour of the frustule on M. V. from N. 
Brébissonii, which in this aspect is linear, not constricted, 
and narrower. 
Hab. Marine. Coast of Northumberland, common in 
sand-gatherings (A. S. D.). 
Navicula rectangulata, Gregory. 
Navicula rectangulata, Greg. Diat. of the Clyde, p.7, pli. fig.7; Ralfs, 
in Prit. Inf. p. 907. 
Pinnularia rectangulata, Rabenh. Europ. Diat. p. 215, 
Plate X. fig. 5. 
Frustule on M. V. oblong, constricted in the middle, extre- 
mities truncate, angles bevelled. VV. linear, bulging 
in the middle and near the broadly rounded extre- 
mities ; strie reaching to the median line, slightly 
shortened around the central nodule, oblique, di- 
verging midway between the central and terminal 
nodules, distinct, costate, 20 in :001”. 
Hab. Marine. Lamlash Bay, Isle of Arran (Prof. Gre- 
gory); coast of Northumberland, common in sand-gather- 
ings (A. S. D.); New Brighton sands and Leasowe sands, 
near Liverpool (Mr. Comber). 
Navicula Trevelyana, Donkin. 
Navicula Trerelyana, Donk. Quart. Mier. Journ. n. s, vol. i. p. 8, pl. i. 
eos Sate Rabenh. Europ. Diat. p. 210. 
Plate X. figs. 6a & 63. 
Frustule elongated, on M. V. broad, oblong, deeply con- 
stricted in the middle, extremities truncate, angles 
