Observations on the diatom genus Fallacia (Bacillariophyta) from southern Brazilian sandy beaches

Members of the genus Fallacia Stickle & D.G. Mann are common epipsammic diatoms on Brazilian sandy beaches (Santa Catarina state). Ten of these species, F. clepsidroides Witkowski, F. florinae (Moller) Witkowski, F. nummularia (Greville) D.G. Mann, F. nyella (Hustedt) D.G. Mann, F. obfuscata sp. nov., F. pygmaea (Kutzing) Stickle & D.G. Mann, F. pseudony (Hustedt) D.G. Mann, F. schoemaniana (Foged) Witkowski, E subforcipata (Hustedt) D.G. Mann, and E vittata (Cleve) D.G. Mann are illustrated and discussed in this paper. F. obfuscata is described as a species new to science. Comparisons to specimens found in other countries and a general discussion on morphological variability within the genus are presented.