An endemic genus of Madagascan spiders (Araneae, Archaeidae, Eriauchenius) is revised. All 20 species of Eriauchenius are described and keyed, of which 14 are new species: Eriauchenius andriamanelo sp. n., Eriauchenius andrianampoinimerina sp. n., Eriauchenius goodmani sp. n., Eriauchenius harveyi sp. n., Eriauchenius lukemacaulayi sp. n., Eriauchenius milajaneae sp. n., Eriauchenius milloti sp. n., Eriauchenius rafohy sp. n., Eriauchenius ranavalona sp. n., Eriauchenius rangita sp. n., Eriauchenius rixi sp. n., Eriauchenius sama sp. n., Eriauchenius wunderlichi sp. n., Eriauchenius zirafy sp. n. Additionally, six species of the new genus Madagascarchaea gen. n. are described and keyed, of which four are new species: Madagascarchaea fohy sp. n., Madagascarchaea lotzi sp. n., Madagascarchaea moramora sp. n., Madagascarchaea rabesahala sp. n. Diagnostic characters for the Madagascan and African genera are described, and based on these characters and previous phylogenetic analyses the following species transfers are proposed: Eriauchenius cornutus (Lotz, 2003) to Afrarchaea; Afrarchaea fisheri (Lotz, 2003) and Afrarchaea mahariraensis (Lotz, 2003) to Eriauchenius. Finally, we propose that the distribution of Afrarchaea be restricted to South Africa. While several Madagascan specimens have previously been identified as Afrarchaea godfreyi (Hewitt, 1919), we argue that these are likely misidentifications that should instead be Eriauchenius.