ABSTRACT
Mineralogical constitution — Microscopical structure — Buenos Ayres, shells embedded in tosca-rock — B. Ayres to the Colorado — S. Ventana — Bahia Blanca; M. Hermoso, bones and infusoria of; P. Alta, shells, bones and infusoria of; co-existence of the recent shells and extinct mammifers — B. Ayres to St Fé — Skeletons of Mastodon — Infusoria — Inferior marine tertiary strata, their age — Horse’s tooth — Banda Oriental — Superficial Pampean formation — Inferior tertiary strata, variation of, connected with volcanic action; Macrauchenia Patachonica at S.Julian in Patagonia, age of, subsequent to living mollusca and to the erratic block period — Summary -Area of Pampean formation — Theories of origin — Source of sediment -Estuary origin — Contemporaneous with existing mollusca — Relations to underlying tertiary strata — Ancient deposit of estuary origin — Elevation and successive deposition of the Pampean formation — Number and state of the remains of mammifers; their habitation, food, extinction, and range -Conclusion — Localities in Pampas at which mammiferous remains have been found.
