Two fossil diatoms (Bacillariophyceae) with exceptional ultrastructural details

This paper discusses morphological details of two fossil diatoms. Closer investigations showed that they belong to other genera than supposed so far. Each of the discussed diatoms shows a morphological detail which is unusual within the respective genus. However, all other structures coincide and the differences have to be considered as special features of extinct ancestors. Encyonema subtriangulum Krammer nom. prov. ist described as a new species within the genus Cymbella and Gomphonema roehringeri E.Reichardt is transfered to the genus Gomphonella.