A very peculiar species which, as Cleve remarks, seems not to be allied to any other. L. about 35 µ, quite constant in size. It is reported from Finland, Scotland, Hungary and New Zealand. Dr. Lewis found it in the Delaware River. It is occasional in the Schuylkill River and the blue clay, and very abundant on Marchantia and mosses on the wet rocks of the upper Wissahickon (F. J. Keeley). Pl. 27, Fig. 17. LINEOLATÆ CL. Valve more or less lanceolate; axial area narrow or indistinct; striæ radiate or parallel, lineate, that is, with the puncta closer than the striæ. NAVICULA RADIOSA KUETZ. Valve lanceolate with sub-rostrate apices; axial area indistinct; central area small; striæ radiate in the middle, from 6 to 8 in 10 µ, and convergent at the ends, about 12 in 10 µ. L. 47 µ. Very common in fresh water. Pl. 26, Fig. 17; Pl. 40, Fig. 9. NAVICULA PEREGRINA EHR. Valve lanceolate, obtuse; axial area narrow; central area large, rounded or slightly irregular; striæ coarse in the middle, 5 in 10 µ, radiate; convergent at the ends, 7 or 8 in 10 µ. Abundant in brackish water. Delaware River. Pl. 26, Fig. 20. {95}NAVICULA CYPRINUS (WM. SM.) Valve lanceolate, slightly gibbous in the middle, sub-cuneate at the ends; axial area narrow; central area small; striæ radiate in the middle, 10 in 10 µ, with shorter, transverse striæ intermediate; transverse at the extreme ends. L. 82 µ. _Navicula digito-radiata_ var. _cyprinus_ (Ehr. ?) Wm. Sm. Whether the form here figured is Ehrenberg's or not, it is the species known as Pinnularia cyprinus Ehr. of Wm. Smith. Common in Shark River, N. J. Pl. 26, Fig. 21. NAVICULA REINHARDTII GRUN. Valve elliptical or elliptical-lanceolate, with broad, rounded ends; axial area narrow, widened at the ends to the width of the valve; central area widened transversely to an irregular, quadrate space; striæ coarse, 8 in 10 µ, distinctly lineate, alternately longer and shorter in the middle, radiate, nearly transverse at the ends. L. 59 µ. Blue clay. Rare. Pl. 26, Fig. 22. NAVICULA LANCEOLATA VAR. ARENARIA (DONK.) CL. Valve lanceolate; axial area very narrow or indistinct; central area small, rounded; striæ radiate, 11 in 10 µ in the middle, closer at the ends. L. 47-54 µ. _Navicula arenaria_ Donk. Shark River, N. J. Pl. 26, Fig. 23. NAVICULA SALINARUM GRUN. Valve elliptical-lanceolate with produced sub-capitate or rostrate ends; striæ radiate in the middle, longer and shorter; transverse at the ends, lineate. L. 32 µ. Atlantic City, N. J. Pl. 26, Fig. 24. NAVICULA VIRIDULA VAR. ROSTELLATA KUETZ. Valve lanceolate with rostrate ends; axial area very narrow, central area orbicular; striæ radiate in the middle, about 12 in 10 µ, convergent at the ends and closer. L. 43 µ. Common in fresh water. Pl. 26, Fig. 16. NAVICULA GRACILIS VAR. SCHIZONEMOIDES (EHR.) V. H.