Cosc. perforatus Ehrenberg

Division: Chromophyta
Class: Bacillariophyceae
Order: Biddulphiales
Suborder: Coscinodiscineae
Family: Coscinodiscaceae Kützing
Genus: Coscinodiscus Ehrenberg
Scientific name: Coscinodiscus perforatus Ehrenberg

Species: perforatus

References:
Cupp, 1943: p. 61; Fig. 25 A, Pl. 3: 1; Hendey, 1964, p. 77.

Description:
Valves flat or slightly convex in the center or sometimes slightly concave. Diameter 90-110 μm. Valves with large areolae forming a closed network, unlike the type in which the areolae are free. Rosette present in center of valve in all individuals observed in the material. Areolae become larger from center toward middle of radius, then smaller again; 4½ in 10 μm in center, 4 midway, and 4½-5 near margin. Inner chamber openings, distinct; outer closing membrane poroid especially on the margins of the areolae. Radial rows of areolae are somewhat more marked than secondary spiral rows. Regular and distinct interstitial mesh placed before the inserted radial rows. Valve margin small, radially striated, striae 8 in 10 μm. Marginal spinulae indistinct, the two asymmetrical processes or apiculi small (Cupp, 1943).

Dimensions:
Valve diameter 100-150 µm.

Distribution:
Pelagic plankton species.

Sites of occurrence in RSA:
This species was occurred at Station 66 (refer site map) and in small numbers at Transects 2a and 6 of northern inner RSA during Leg 3 of the Winter 2006 Cruise.