From a collection of millipeds made in Limon Province new locality records for 13 established species are given; descriptions, figures, and as extensive keys as possible are given for 15 n. spp. in 7 families; 1 sp. represents a n. gen. of chytodesmid. Cyrtodesmus laticaudatus n. sp. from Panama is described and figured. Siphonophora costaricae Chamberlin is redescribed and figured, and his S. valeri is placed as a new synonym under it.