Valve lanceolate, gently tapering to the obtuse, produced ends; axial area lanceolate, widened to an orbicular space in the middle; striæ radiate, the median coarse and quite distant, 5 in 10 µ, becoming closer at the ends where they are 12 in 10 µ, lineate. The distance between the median striæ gives the appearance of a stauros. Occasional in the blue clay. Pl. 27, Fig. 13. NAVICULA HASTA VAR. PUNCTATA N. VAR. Valve as in type but with striæ in the middle distinctly punctate and reaching the median line. Greenwich Point, Philadelphia. Pl. 27, Fig. 14. NAVICULA RHYNCOCEPHALA KUETZ. Valve lanceolate, with produced ends; axial area indistinct; central area small, rounded; striæ radiate in the middle, convergent at the ends, 10-11 in 10 µ, punctate. L. 42 µ. Fresh water. Common. Pl. 31, Fig. 8. NAVICULA CRYPTOCEPHALA KUETZ. Valve lanceolate, with rostrate ends; axial area indistinct; central area small; striæ, 16 in 10 µ, lineate, radiate in the middle, convergent at the ends. L. 28 µ. Common in fresh water. Intermediate forms occur between N. rhyncocephala and N. cryptocephala. Pl. 31, Fig. 9. NAVICULA LONGA (GREG.) RALFS Valve slender, rhombic, elongated, with acute ends; axial area indistinct; central area small; striæ, 6 or 7 in 10 µ, radiate in the middle, elsewhere transverse; central pores closely approximate. L. 120 µ. New Rochelle, N. Y. Pl. 31, Fig. 10. Cleve refers this form to N. directa var. remota Grun. Some specimens are found in this locality showing the "generally twisted" median line mentioned by Gregory. MESOLEIÆ CL. Valve linear or elliptical; axial area narrow; central area quadrate; striæ radiate, finely punctate. NAVICULA MUTICA KUETZ. Valve ovate, elliptical or lanceolate; axial area narrow; central area dilated into a stauros not reaching the margin; striæ about 20 in 10 µ, more distant in the middle, radiate, punctate. A punctum occurs on one side of the central nodule. {98}Reported from New Jersey in fresh water. I have not found it. The figure is from a specimen from another locality. Pl. 26, Fig. 6. NAVICULA MINIMA GRUN. Valve broadly elliptical, 13-15 µ in length; axial area narrow; central area small but with a quadrate pseudo-stauros which is striated; striæ, about 28 in 10 µ, radiate. Agrees closely with N. saugeri var. Grun. in V. H. Synopsis, Pl. 14, Fig. 16, said to be intermediate between N. minima and N. atomoides Grun. N. minima var. atomoides Grun. is smaller. Common in water-troughs. Pl. 26, Fig. 13. NAVICULA PUPULA VAR. BACILLARIOIDES GRUN. Valve linear, with rounded ends; axial area linear, expanding on both sides near the ends of the valve, forming a transverse lunate space; central area small, apparently expanded into a stauros, which, however, is striated; striæ, 18 in 10 µ, at the middle, closer at the ends, punctate. L. 54 µ. Pavonia, N. J., artesian well. Pl. 26, Fig. 9. BACILLARES CL.