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.