XVI International Botanical Congess

Samples of the Coscinodiscus jonesianus (Grev.) Ostenf. complex from Florida, W. Africa, Sumatra and China were studied. The complex includes large centric diatoms with two pronounced elevations, each containing a macrolabiate process, a marginal ring of microlabiate processes, and, sometimes, a hyaline radial line on the valve. We recognize seven taxa in this complex, including two undescribed forms. They differ in diameter, size of areolae, distance between microlabiate processes, and in the presence of spines, siliceous granules and an intermediate ring of labiate processes. Other coscinodiscoid diatoms have similarities, but not in this unique combination. Either the removal of this species complex from the genus or the expansion of the generic and family limits may be warranted.