Valve nearly symmetrical, lanceolate, with rostrate, produced apices; median line nearly straight; axial area linear, widened in the middle; striæ radiate, punctate. Blue clay. Pl. 18, Fig. 10. CYMBELLA CUSPIDATA KUETZ. Valve broad, elliptical, with rostrate, somewhat acute, apices and nearly straight, ventral margin; median line straight, axial area linear, widened in the middle; striæ radiate, punctate. Blue clay. Pl. 18, Fig. 17. CYMBELLA NAVICULIFORMIS AUERSWALD Valve linear-elliptical, with abruptly produced apices; ventral margin straight; median line almost straight; axial area narrow, central area large, rounded; striæ distant in the middle, closer at the ends. Fresh water. Pl. 18, Fig. 6. CYMBELLA EHRENBERGII KUETZ. Valve lanceolate, with ventral margin nearly straight and apices sub-rostrate; median line straight, excentric; axial area narrow; central area widened in the middle; striæ coarsely punctate. Fresh water. Pl. 18, Fig. 9. {61}CYMBELLA AFFINIS KUETZ. Valve about three times as long as broad, strongly convex on the dorsal side and straight on the ventral; apices sub-rostrate; striæ punctate; axial area narrow, not widened in the middle; median line curved; a small or indistinct punctum on the ventral side of the median line (not shown in the figure). Common in ponds. Abundant in East Park Reservoir. Pl. 18, Fig. 18. CYMBELLA EXCISA (KUETZ.) DE TONI Valve as in affinis, but with tumid and excised ventral margin; a punctum is found on the ventral side (not shown in the figure). According to Cleve this is a variety of C. affinis. Common in ponds. Pl. 18, Figs. 15, 19? CYMBELLA PARVA (WM. SM.) CL. Valve semi-lanceolate, with produced apices; ventral margin slightly tumid; axial area narrow; striæ coarsely but obscurely punctate. C. affinis and C. parva are quite variable, the latter differing by its lanceolate form and the absence of a punctum, which, however, is sometimes difficult to recognize. In a gathering of C. parva, it is quite possible to find numerous abnormal forms which appear to be sporangial, so that specific distinctions are difficult if based on occasional specimens. Common in ponds. Pl. 38, Fig. 14. CYMBELLA AMPHICEPHALA NÆGELI Valve unequally elliptical, with broad, rostrate apices; axial area narrow; median line straight; central area small, rounded; striæ, 12 in 10 µ on the dorsal, closer on the ventral, side and at the ends. Kirkwood Pond, N. J. Pl. 18, Fig. 16. CYMBELLA SINUATA GREG. Valve linear-elliptical, gibbous on the ventral side; axial area indistinct; central area widened on the ventral side nearly to the margin. Crum Creek. Pl. 18, Fig. 13. SECTION 2.--COCCONEMA. FRUSTULES STIPITATE CYMBELLA ASPERA (EHR.) CL.