1	Valve shapes semi-lanceolate dorsiventral	2
1a	Valve shapes lanceolate dorsiventral	9
2	Valve length 6–20 μm	3
2a	Valve length 8–26 μm	8
3	Ventral margin straight	4
3a	Ventral margin curved	C.brotasiae
4	Internal valve has one thickening silica	C.decusa
5	Striae density 40–50 in 10 μm	C.densestriata
6	Striae density < 40 in 10 μm	C.adhaerens
6a	Transapical striae coarse	C.robusta
6b	Raphe eccentric along the edge of valve face	C.javanica
7	Striae density ~ 90 in 10 μm	C.exigua
8	Raphe eccentric on the ventral valve face	C.boyanensis
8a	Valve long 23–38 μm, wide 6–11 μm	C.pelagica
9	Internal valve has two thickening silica	C.komodensis