Three species of the millipede family Platyrhacidae from Costa Rica: a new Barydesmus Cook, 1896 and two oldest Nyssodesmus Cook, 1896 (Diplopoda, Polydesmida).

Three species of Platyrhacidae from Costa Rica are treated and illustrated in due detail: Barydesmus truncatus sp. nov., Nyssodesmus alboalatus Cook, 1896, and N.

The milliped family Platyrhacidae (Polydesmida: Leptodesmidea) in the West Indies: Proposal of Hoffmanorhacus n. gen.; description and illustrations of males of Proaspis aitia Loomis, 1941; redescription of Nannorrhacus luciae (Pocock, 1894); hypotheses on origins and affinities; and an updated New World familial distribution.

In the New World, the milliped family Platyrhacidae (Polydesmida) is known or projected for Central America south of southeastern Nicaragua and the northern ¼ of South America, with disjunct, insular populations on Hispaniola (Haiti), Guadeloupe (Basse-Terre), and St. Lucia. Male near-topotypes enable redescription of Proaspis aitia Loomis, 1941, possibly endemic to the western end of the southern Haitian peninsula.