Twenty species of Symphypleona are recorded from the Gambia of which twelve are new to science and are described. A brief survey is given of the chief vegetation and soil types to assist in classifying the habitat references in the text. Sminthurinus stenognathus Börner and Bourletiella spathacea Börner are noted as probably extending throughout the northern savanna belt of the Ethiopean region, having been recorded from both ends of this vegetation zone. Sminthurides cf. ramosus and Sminthurus macroceros Denis are recorded as occurring on both sides of the Atlantic and it is suggested that resistant stages which allow them to live under savanna conditions also fit them for long distance wind dispersal. In an appendix (vide infra) some information is given on some species of Sminthurides for comparison with species newly described here, and lectotypes are established for S. melanotus and S. spegazzinii from material in the British Museum collection.