Four new species of troglobitic millipedes are described from central Texas caves: Speodesmus castellanus from Fort Hood, Bell and Coryell counties; S. falcatus from Camp Bullis, north central Bexar County; S. reddelli from Government Canyon State Natural Area, Helotes and other points in northwestern Bexar and northeastern Medina counties; and S. ivyi from Camp Bullis and San Antonio, Bexar County, and Comal County. The closest relative of S. castellanus is S. bicornourus, from caves in Williamson, Travis, and Burnet counties, Texas. Speodesmus falcatus and S. reddelli are relatives of S.
echinourus, which is distributed across the Edwards Plateau and parts of the Balcones Escarpment, central Texas. Speodesmus ivyi is similar to Speodesmus n.sp. 1, Val Verde County. Some characters previously thought to distinguish species groups of Speodesmus may be unsuitable for separating groups within the genus.