EPITHEMIA MUELLERI A. S. ? Valve broad, convex, slightly arcuate, with obtuse, somewhat constricted apices; costæ about 4 in 10 µ; striæ, 12-14 in 10 µ; in zone view the outline is rectangular, slightly tumid in the middle. L. 78 µ. Blue clay. Pl. 31, Fig. 17. {112}EPITHEMIA ZEBRA VAR. PROBOSCIDEA (KUETZ.) GRUN. Valve convex on the dorsal, concave on the ventral side; costæ, 3-4 in 10 µ, slightly radiating; apices recurved, capitate. Blue clay. Pl. 31, Fig. 18. EPITHEMIA GIBBERULA VAR. PRODUCTA GRUN. Valve narrow, lunate, with produced and arcuate apices; costæ radiate, 3-4 in 10 µ; striæ, 16-18 in 10 µ, punctate. L. 58 µ, usually smaller. Blue clay. Pl. 31, Fig. 19. EPITHEMIA MUSCULUS KUETZ. Valve short, strongly arcuate on the dorsal, concave on the ventral side; apices slightly produced; costæ radiate, about 5 in 10 µ; striæ, 15 in 10 µ, punctate. L. 20-60 µ. Shark River, N. J. Pl. 31, Fig. 20. EPITHEMIA MUSCULUS VAR. CONSTRICTA (BRÉB.) V. H. Frustule elliptical, slightly constricted in the middle. Valve convex on the dorsal, straight on the ventral side; costæ about 4 in 10 µ; striæ about 18 in 10 µ, finely punctate. L. 45 µ. _Epithemia succinta_ Bréb. New Rochelle, N. Y. Pl. 31, Fig. 22. RHOPALODIA MUELLER (1885) (Rhopalodes, like a war club) Frustule in zone view linear, linear-elliptical (in our species), or clavate. Valve reniform or lunate; a raphe, not visible in some species in the usual position of the valve, is found along the convex edge or keel. Median and terminal nodules, although very small, can be determined. The name is more appropriate to the African species which are clavate. Two species only are found in this locality. The chief distinction between Epithemia and Rhopalodia is in the position of the raphe and the nodules. In R. gibba and R. ventricosa the costæ are parallel and not radiate since the valves are not lunate. Chromatophore a single band irregularly divided. RHOPALODIA GIBBA (KUETZ.) MUELLER Valve linear, arcuate on the dorsal, straight on the ventral side, reflexed at the extremities. Costæ, 6-7 in 10 µ; striæ about 14 in 10 µ. L. 80-200 µ. Fresh water. Common. Pl. 31, Fig. 23. In this species the raphe and nodules can be seen only when the valve is examined at right angles to its usual position. {113}RHOPALODIA VENTRICOSA (KUETZ.) MUELLER Valve gibbous in the middle on the dorsal side, straight on the ventral side, with reflexed apices; costæ, 7 in 10 µ; striæ, 14-16 in 10 µ. L. 40-100 µ. The median nodule appears as a minute depression in the middle of the dorsal side. The two species usually occur together. _Epithemia gibba_ var. _ventricosa_ Kuetz. Pl. 31, Fig. 24. SURIRELLOIDEÆ