Pl. [23], Fig. 1.
GYROSIGMA KUETZINGII (GRUN.) CL.
Valve sigmoid, lanceolate, with sub-acute ends; raphe central, the central nodule elliptical; transverse striæ, 21-23, and longitudinal, 25-26 in 10 µ.
Pleurosigma spencerii var. acutiuscula Grun.
Pleurosigma spencerii var. kuetzingii Grun.
Common in fresh water.
Pl. [38], Fig. 12.
GYROSIGMA SCALPROIDES (RAB.) CL.
Valve slightly sigmoid, with obtuse ends; raphe nearly straight; central nodule elliptical; transverse striæ, 22, slightly radiate and more distant in the middle; longitudinal striæ, 29 in 10 µ. L. 60 µ.
Common in streams.