THE TAXA OF FOSSIL MOLLUSCA INTRODUCED BY VONIHERING,HERMANN

Between 1896 and 1921 Hermann von Ihering described or named 352 taxa of fossil molluscs, from genera to subspecies, and many ''varieties.'' Most of the taxa were from southern Argentina (Patagonia), bur some w ere from Chile, Uruguay, and Brazil. When combined with other species described by Arnold E. Ortmann in 1902, these fossils constitute the b asis of our knowledge of the Tertiary malacofauna of the region. Iheri ng's collection was acquired in 1920 by the Museo Argentino de Ciencia s Naturales, and during the 1940s the author organized and catalogued the collection of more than 900 lots. This paper deals with Ihering's taxa and: 1) updates the taxonomic nomenclature for both genera and sp ecies; 2) indicates the correct type localities, many of which were un certain at the time of description; 3) clarifies the stratigraphic pos ition and geologic age of the deposits where the fossils were found; a nd 4) reconsiders some of Ihering's conclusions about the origin and d istribution of the fauna in relation to climatic changes in the region during the Tertiary. Ihering's stratigraphy overestimated the age of deposits. There were no intercalations between the Cretaceous and Eoce ne; Paleocene species were believed to be Cretaceous; marine formation s of the Miocene were dated as Eocene, and so on. He also subdivided f ormations in order to indicate that parts of them were older. The rela tive ages of strata were based on the proportion of extinct species ve rsus surviving ones. When synonyms are recognized, and many infrasubsp ecific names eliminated as nontaxonomic variations, such estimation is untenable. Most of the mid-Tertiary species belong to genera that are represented in the Recent, and from zones warmer than the present cli mate in the Patagonian and Magellanian regions. Climatic changes were not local phenomena bur the consequence of plate tectonics. Movements of plates not only changed their location, but also the orientation of the masses of land by clockwise rotation. The plates, formerly separa ted, united into a new continent, and rotation reversed to countercloc kwise bringing them into their present position. Ihering considered th em a single, unique mass, and named them Archhelenis (the northeastern part including Brasilia) and Archiplata (the southwestern part). Alth ough land-bridge theories have been replaced by interpretations from p late tectonics, Ihering's nomenclature for the land masses is still us eful and valid. New combinations are proposed for 32 species, and lect otypes are designated for Mactra indistincta Ihering (1897), Neoinocer amus ameghinoi Ihering (1902), Nucula tricesima Ihering (1897), Phacoi des rocana Ihering (1907), Panopea thomasi Ihering (1914), and Potamid es pnragonensis Ihering (1897). Aturia (Sphenaturia) brueggeni Ihering , 1921, is selected as the type species of Sphenaturia Ihering, 1921 ( Nautilidae).