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.
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.