Family: Coscinodiscaceae Kützing
Genus: Coscinodiscus Ehrenberg
Scientific name: Coscinodiscus janischii Schmidt var. arafurensis Grunow
Hustedt, 1930: p. 461, Fig. 257; Allen and Cupp, 1935: p. 120, Fig. 17 a-d.
Cell disc-shaped, with almost flat valves,slightly depressed in the center. Central area small, but distinct. A row of small areoles near the margin, about 4 in 10 µm; around the central area 2½ to 3 in 10 µm; on rest of surface valve of nearly equal size, about 2 in 10 µm. Valve hyaline in appearance. Radial and secondary spiral rows, distinct. Valve margin small, with radial striae, about 5-6 in 10 µm. Diameter 170-261 µm (Allen and Cupp, 1935).
Valve diameter 220-245 µm.
Subtropical and tropical waters.
Sites of occurrence in RSA:
In Winter 2006 Cruise, this species occurred at different sites (refer sites map) in small numbers; maximum abundance (1.5*10^2cells/l) was associated with the Iranian coast in thecentral part of the inner RSA (St. 40).