Diatom Monographs: Volume 6: Amphorotia nov. gen., a new genus in the

• Description

The new genus Amphorotia is described based on Eunotia clevei Grunow in Cleve et Grunow 1880. The genus is defined by a complex of morphological characters, notably the amphoroid shape of the frustule, details of the siliceous structure of the valve and girdle, and size and orientation of the raphe and rimoportulae. The genus belongs in the family Eunotiaceae and its relationships with other members are discussed.

Fourteen species are described, of which 6 are new to science. Of these 14, Amphorotia clevei is a cold water boreal species, 5 are endemic to lake Baikal, Siberia, 1 is endemic in Lake Hovsgol, Mongolia, 4 appear to occur only in South East China - often associated with marine to brackish water, and 3 are believed to be extinct, known only from Miocene fossil specimens, of which one deposit is marine. In addition, 5 other species are included in the genus based on published information. The geographic distribution of the species is also discussed, particularly with reference to the two patterns shown by these species, one extending across the Northern boreal, the other into more tropical regions via Southern China.