Two new species of the genus Mastogloia are described. Mastogloia sawensis sp. nov. and M. vestigiostriata sp. nov. were encountered as epiphytes on Chara sp. which covers the sediment of Sawa Lake, an isolated saline water body in southern Iraq. Mastogloia sawensis belongs to the section Lanceolatae and is closely similar to M. lanceolata but differs in raphe curvature, areolae shape and arrangement, and the presence of rounded pores at the junction of the partecta. Mastogloia vestigiostriata resembles under light microscopy to M. lyra and M. braunii but shows differences in several features including valve mantle structures, H-shaped lateral hyaline area, siliceous flanges and partectal formation. This study gives morphological details on the ultrastructure of the new species and provides a detailed comparison with all related taxa.