Four new species of the genus Cymadusa are described from Brazil (states of Ceará, Espírito Santo and Rio de Janeiro). Cymadusa icapui is described from Ceará state, C. trindadensis is described from Espírito Santo state, C. rasae and C. tartarugae are described from Rio de Janeiro state. Two identification keys are presented: one to all known species of the family Ampithoidae from Brazil, and another one to world species of Cymadusa. Based on literary review and analysis of collection material, we extend the distribution of Cymadusa filosa Savigny, 1816 along the Brazilian coast by finding new location records of the species based on analysis of stored collection material.
Keywords: Crustacea, taxonomy, Ampithoidae, Brazil, shallow waters, identification key.