Abstract
This paper presents detailed morphological descriptions of three small Navicula species that occur rather abundantly in the brackish Baltic Sea, and probably also in brackish waters elsewhere. Two of these, N. sjoersii and N. bossvikensis, are described as new taxa. A morphologically similar species, N. perminuta Grunow, is presented as well because it may easily be confused with N. sjoersii and other related taxa.