Cenozoic marine deposits of forearc basins in southern Peru contain a molluscan fauna that includes 15 species of turritelline gastropods. Twelve species were previously known; ten from northern Peru or Chile and two species solely from southern Peru. Three new fossil species are described: Turritella riverae, Turritella cruzadoi, and Turritella salasi. Six species of turritellines with crenulated primary spirals, a distinctive spiral ontogeny, and which are mostly endemic to Peru and Chile, are assigned to Incatella n. gen., including I. cingulata (Sowerby, 1825), I. cingulatiformis (Möricke, 1896), I. chilensis (Sowerby, 1846), I. leptogramma (Philippi, 1887), I. hupei Nielsen, new name (=Turritella affinisHupé, 1854), and I. trilirata (Philippi, 1887). Most Paleogene taxa range from northern to southern Peru, while most Neogene taxa, including all species of Incatella, range from Peru to Chile. This biogeographic asymmetry is attributed to a series of biotic events (e.g., extinctions, immigrations) impelled by global oceanographic changes acting locally in a regime of coastal upwelling.