Abstract
The scale case of the auxospores of Coscinodiscus granii is composed of two types of scales: the typical scale type, found commonly in auxospores, and constituting the majority of the cell's investment, and intermingled, a limited number of scales possessing a clear slit in the central area circumscribed by the annulus. Their sum approximates the sum of the rimoportulae in a valve (63–65) of this species. It is suggested that they may be the pre-stages of the rimoportulae in Coscinodiscus.