Hustedt, 1930: p. 436, Fig. 237;Cupp, 1943: p. 57, Fig. 21; Crosby and Wood, 1958: p. 496, Pl. 36: 17;Hendey, 1964: p. 79; Simonsen,1974: p. 16; Throndsen et al., 2007:p. 150.
Cells with eccentric arched valves;one side of cell almost twice as high as the other. Diameter 95-190 µm.Central areolae in a definite rosette. About 8 areolae in 10 µm near center, 10 midway to margin, and 11 near margin; on edge of valve mantle 13 in 10 µm. Chamber openings small,dotlike. Outer closing membrane of areolae very delicately poroid. Radial rows and secondary spiral rows distinct. Marginal spinulae and the hyaline lines radiating from the spinulae toward the center distinct, 5-7 µm apart. Two small processes or apiculi on margin at distance of about 120° from each other. Girdle formed from the two similar girdle bands. Nointercalary bands (Cupp, 1943).
Valve diameter 85-120 µm.
Neritic, widely distributed; north temperate or boreal species. It has been previously reported from the Indian Ocean (Simonsen, 1974).
Sites of occurrence in RSA:
In Winter 2006 Cruise, this species occurred at various sites (refer sites map) in small numbers; maximum abundance (1.2*10^2cells/l) was associated with the northwestern part of the inner RSA off Saudi Arabia (St. 23). It has been previously reported from Kuwaiti watersof the inner RSA (Al-Yamani et al., 2004; Al-Kandari et al., 2009).