Pycnogonida from the SEPBOP Expeditions and additional unreported specimens from other collections are described. They contain 30 described species, with an additional 10 newly described and 4 undescribed for lack of suitable specimens. The newly described species are Ammothea insularis, Ascorhynchus comatum, A. paxillum, Prototrygaeus contrarius, Tanystylum cinctum, Pallenopsis (P.) notiosa, P. (P.) truncatula, Nymphon similis, Anoplodactylus bruuni, and A. vulcanus. Five additional known species are refigured or figured for the first time to clarify their validity and they are redescribed where necessary. These species are Ammothea dorsiplicata (Hilton), Ammothella heterosetosa Hilton, Eurycyde longisetosa Hilton, E. spinosa Hilton, Pycnothea selkirki Loman, and Rhynchothorax barnardi Child and Hedgpeth. Previous literature on South American Pacific pycnogonids is reviewed and the zoogeography of each species is discussed.
