A new genus, Pseudodysderina, is established for a group of species that resemble those of Dysderina Simon in having grooves connecting both the anterior and posterior spiracles. These spiders have transverse ridges on the sternum but lack the sternal excavations that characterize Dysderina and are instead united by the highly modified mouthparts of males: the labium is greatly enlarged, with a dorsoventrally flat, posterior portion that extends far posterior of the anterolateral corners of the sternum, and the endites are each deeply excavated, medially around the sides of the labium and laterally around the base of the palpal trochanter. Dysderina desultrix (Keyserling), from Peru, is transferred to Pseudodysderina and chosen as the type species; its male is described for the first time. This species has been taken by canopy fogging and beating foliage as well as in leaf litter, and appears to be widespread in the Amazonian portions of Colombia, Ecuador, Peru, and Brazil. Seven more narrowly distributed new species are described from Peru (P. manu), Bolivia (P. yungas, P. beni), Ecuador (P. hermani), Colombia (P. suiza, P. dracula), and Brazil (P. utinga). The six new species assigned to the new genus Tinadysderina resemble those of Dysderina and Pseudodysderina, but have a much smaller, simpler, weakly sclerotized embolus; they are known only from the western slopes of the Andes in Ecuador (T. tinalandia, T. otonga) and Colombia (T. planada, T. gorgona, T. bremen, T. pereira).