Valve oblong-elliptical or elliptical-lanceolate, with sub-cuneate ends; axial area lanceolate, widened in the middle to an orbicular space; striæ radiate, 7 in 10 µ, puncta, 11 in 10 µ, the median striæ alternating with short striæ along the sides. L. 50-150 µ (Cl). Blue clay. Pavonia, N. J., artesian well. Pl. 24, Fig. 3. {91}NAVICULA LATISSIMA VAR. ELONGATA (PANT.) CL. Valve elliptical-lanceolate, with rounded ends; striæ and puncta closer than in the type form; axial area narrow, widened in the middle; terminal fissures hook-shaped, turned in different directions. _Navicula humerosa_ var. _elongata_ Pant. Fossil at Buckshutem, N. J. Pl. 24, Fig. 5. NAVICULA FUCHSII PANT. Valve elliptical, with slightly produced apices; axial area wide, lanceolate; central area orbicular; striæ alternately longer and shorter in the middle, 10-12 in 10 µ; puncta on the border of the axial area larger, elongated; median fissures incrassate. _Navicula humerosa_ var. _fuchsii_ (Pant.) Cl. _Navicula_ (_latissima_ var.?) _fuchsii_ Pant. Port Penn, Delaware River. Pl. 24, Fig. 6. NAVICULA HUMEROSA BRÉB. Valve lanceolate-elliptical or oblong-elliptical, with sub-cuneate or sub-rostrate ends; axial area narrow, lanceolate; central area rounded, somewhat transverse; terminal fissures hook-shaped, in the same direction; central pores incrassate; striæ, 11 in 10 µ, the middle alternately longer and shorter, closer at the ends. L. 60-86 µ. Variable in size, outline and fineness of striation. N. monilifera Cleve (N. granulata Bréb.) differs in having coarser striæ. Blue clay. Along the coast. Pl. 25, Fig. 5. NAVICULA PUSILLA WM. SM. Valve ovate-elliptical, with rostrate or sub-rostrate ends; axial area narrow; central area elliptical; striæ radiate, 10-12 in 10 µ in the middle where they are longer and shorter alternately, closer at the ends; median fissures somewhat incrassate, terminal in the same direction. L. 47 µ. Smith's Island, Delaware River. Pl. 25, Figs. 4, 6? Cleve gives the striæ as 13-18 in the typical form, and 11-13 in varieties. In the form here figured the striation is as stated by De Toni, but is about 19 at the ends. Fig. 6 appears to be a small form of N. pusilla, near lanceolata Grun., at least according to the figure in "Arctic Diatoms," but not Gregory's figure. It occurs rarely in fresh water at Newtown Square. It may be a small form of N. punctulata and, if so, is probably accidental, as the material is entirely fresh-water. NAVICULA PUSILLA VAR. SUBCAPITATA N. VAR. Valve elliptical with rostrate-capitate and truncate ends; striæ about 12 in 10 µ in the middle where they are unequal; axial area narrow, slightly widened in the middle; central pores incrassate, terminal fissures in the same direction. Differs from type in outline and centre. Pavonia, N. J., artesian well. Rare. Pl. 25, Fig. 8. {92}NAVICULA DELAWARENSIS GRUN.