Three species of Trogontherium have existcd in Eurazia. The geologically oldest is the beaverrat-sized Upper-Pliocene Trog. minus Newton of the lowest strata (Nodule Bed) of the Red Crag in East-Anglia and in the Astian fauna of Roussillon. It also occurred in Siberia. The type skull of the beaver-sized Trog. boisvilletti (Laugel) has been found in St. Prest, near Paris, and all the isolated skeleton bones are known from the Trogontherium Clay of Tegelen in the Netherlands, where this gnawer was abundant among an Upper-Villafranchian fauna (Archidiskodon meridionalis, (archaeic type), Eucladoceros, Sus strozzii, Leptobos, Mimomys pliocaenicus, etc.) of the Günz-interstadium. Of the third species, Trog. cuvieri Fischer, the jaws and teeth were distinctly larger and the skull more specialized by the existance of a ductus pneumaticus cranii, similar to that of the American Castoroides. The sands of Mosbach yielded the richest material of this species. The generic name of Amblycastor (MATTHEW, 1918) has to give way to that of Anchitheriomys (ROGER, 1898) for the beaver-sized Upper-Miocene castorid of the holarctic area, because the diagnosis of the genus Amblycastor (STIRTON, 1935) fits exactly Anchitheriomys the knowledge of which has been considerably augmented by SEEMANN (1938).