Valve linear or linear-elliptical, with broad ends; axial area narrow, the median line enclosed in siliceous ribs; striæ finely punctate, more distant in the middle. NAVICULA BACILLUM EHR. Valve linear, with rounded ends; axial area enclosed in siliceous ribs and slightly expanded on each side at the ends; terminal nodules incrassate; central area small, elliptical; striæ, 15 in 10 µ in the middle, transverse, distinctly punctate, closer at the ends L. 47 µ. Fresh water. Pl. 26, Fig. 10. Cleve describes the form as having slightly radiate striæ in the middle. There is considerable difference in the descriptions of Cleve, Donkin, Grunow and Van Heurck, as also in all of the figures. NAVICULA AMERICANA EHR. Valve oblong-linear, with rounded ends, sometimes slightly constricted; axial area about one-half the width of the valve, dilated in the middle; striæ parallel in the middle, radiate at the ends, 15-16 in 10 µ. A punctum is usually found in the central nodule. L. 55-154 µ. Blue clay. Occasional in fresh water. Pl. 26, Fig. 8. DECIPIENTES CL. Valve lanceolate, with obtuse ends; axial area narrow; central area orbicular; striæ radiate in the middle and more distant. NAVICULA SEMEN EHR. Valve elliptic-lanceolate, with sub-rostrate, truncate apices; axial area narrow, {99}sinuous; central area orbicular; terminal fissures small, hook-shaped; striæ robust, 7 or 8 in the middle, closer at the ends, indistinctly punctate or lineolate. Blue clay. Not common. Pl. 26, Fig. 11. Cleve states that this form belongs to the post-glacial deposits and is found living only in the Hartz Mountains. NAVICULA INTEGRA WM. SM. Valve lanceolate with triundulate margins and rostrate-apiculate ends; striæ radiate, more distant in the middle, 20-23 in µ, punctate; axial area very narrow, central area rounded or elliptical. L. 33-43 µ. Pavonia, N. J., artesian well. Common in Chester River, Md. Pl. 26, Fig. 5. MICROSTIGMATICÆ CL. Valve lanceolate; axial area narrow; central area small, rounded; striæ finely punctate, nearly parallel. (Includes here only the division Libellus.) NAVICULA TUMIDA (BRÉB.) CL. Valve lanceolate, with rounded ends; axial area narrow, central area elliptical; raphe slightly sigmoid; striæ, 13 in 10 µ, finely punctate, a few shorter in the middle. _Scoliopleura tumida_ (Bréb.) V. H. Cape May, N. J. Pl. 25, Fig. 1. NAVICULA GREVILLEI (AG.) CL. Frustules in gelatinous tubes, rectangular; zone with numerous longitudinal divisions. Valve elliptical-lanceolate, obtuse; axial area narrow, central area small; striæ lineate, about 18 in 10 µ in the middle where they are slightly radiate and more evident, closer near the ends and transverse; median line with terminal pores distant from the ends. L. 60 µ. _Schizonema grevillei_ Ag. East River, N. Y. Pl. 31, Figs. 3 and 4. NAVICULA LIBELLUS GREG.